Outlook Global Customer Service & Support Team Blog articles

Planning considerations for REST-based (aka new model) calendar sharing in Outlook

Will_Loudermilk — Tue, 21 Nov 2023 17:20:04 GMT

Calendar sharing in Microsoft Outlook is a feature many users rely on daily to manage their manager or team calendars. Microsoft has recently made some big changes to calendar sharing in Outlook and there are some key differences between the old calendar sharing model (which uses MAPI) and the new calendar sharing model (which uses REST). The intent of this blog is to inform IT Messaging Admins of the key differences when considering whether to stay with the move to the new REST model or roll back to the old MAPI model.

Important The shared calendar improvements are automatically enabled for Current Channel and Monthly Enterprise Channel starting with version 2112, and for Semi-Annual Enterprise Channel starting with version 2202. To determine if you are using the new calendar sharing model, see the Microsoft Support articles Calendar sharing in Microsoft 365 and Outlook calendar sharing updates.

The MAPI Model

First, let's talk about the MAPI model. MAPI has been used for calendar sharing in Outlook for a while and has remained largely unchanged for approximately twenty years.

Typically, these are the two most common configuration issues we see with the MAPI model:

A single manager granting editor rights to multiple delegates (only one editing delegate is supported under the MAPI model)
Conflicting permissions granted to the delegate for a given manager (example: a delegate was granted both delegate access from the Outlook client and Full Access mailbox permissions from Exchange to their manager's calendar)

These two common configuration issues are documented in the following articles:

The REST Model

The new calendar sharing model based on REST is designed to avoid MAPI issues related to conflicting permissions and multiple editing delegates. This is one of the benefits of the new REST calendar sharing model and may be a reason to use the new model.

That said, there are also some things that you could do in the old calendar sharing model that you cannot do (at least not yet) in the new model, such as the following:

Adding attachments when responding to a meeting invitation
Saving drafts of meeting updates in order to send them out later
Adding the same calendar to multiple calendar groups
Rely on the offline folder item count to match the server item count. This is due to how the calendar is stored in the delegate's mailbox. For more information, see the Calendar sharing in Microsoft 365 article referenced in the first bullet point below.

For more information on other functional differences and best practices for REST-based calendar sharing, see the following articles:

The Calendar sharing in Microsoft 365 article also provides technical details regarding the architectural differences between the old and new calendar sharing models.

Understanding Some of the Key Differences Between the MAPI and REST Models

This section uses diagrams and a numbered list to supplement existing documentation, highlighting some of the key differences between the old and new calendar sharing architectures.

The numbered list shows how some of the key features differ between the old and new models. Each number correlates to a specific design difference. Numbers ❶ and ❷ appear in both the old and new diagrams to highlight how the architectural differences affect that key function. Number ❸ is completely new for REST.

Note The below diagrams assume that the Outlook client is configured to use Cached Exchange Mode with a copy of the mailbox stored locally in the Outlook Offline Data (.ost) file.

❶ In the old MAPI model, the delegate's Outlook client reads/writes (or synchronizes) directly to the principal's Calendar. As more and more delegates are granted access to the principal's Calendar, the likelihood of having the calendars contain outdated, stale, or out-of-sync data increases. In the new REST model, the service intercepts each delegate's attempt to write to the principal's Calendar. Since the service intercepts and handles all attempts to write to the principal's Calendar, the likelihood of conflicting calendars is greatly reduced.

❷ In the old MAPI model, meeting attendees may receive their meeting invitations before the principal's Calendar is updated. This results in the attendee and principal's calendars being out-of-sync. In the new REST model, only the service is responsible for processing changes to the principal's Calendar, handling and sending the meeting invitations to the attendees. This ensures that the principal's Calendar is updated before the attendees can accept the meeting invitation and add it to their own calendars.

❸ In the new REST model, a copy of the principal's Calendar is stored in the delegate's mailbox. This allows the delegate to view it from any of their Outlook mobile devices.

The two-way gold arrows in the old MAPI model diagram highlight the back and forth read/writes that increase the likelihood of conflicting or out-of-sync calendars. In the new REST model diagram, you can see how the likelihood of out-of-sync calendars is greatly reduced (if not altogether mitigated) by having a one-directional sync, as depicted by the series of gold, counterclockwise circular arrows.

Known Issues

You may see negative performance impact in both sharing models when approaching certain item and folder counts as specified in the following article:

Performance issues for too many items or folders - Outlook | Microsoft Docs

There are other known issues with REST-based calendar sharing that you should be aware of. The Outlook team is currently investigating these issues and will update the below article when more information becomes available:

Known issues with Outlook Desktop Shared Calendar Improvements (microsoft.com)

New location for the Mail, Calendar, People, and other modules

abdias_ruiz — Thu, 09 Nov 2023 22:03:11 GMT

Since this blog is a Support blog, the focus of this post is two-fold. First, to advise of changes that the product group is rolling out –including continuing updates to the feature– with key dates and production build information related to said updates. And second, to provide support guidance related to the feature, such as customizations, etc.

Although the support team does not develop features, we do ensure that your and other customers' feedback reaches the relevant product groups, those ultimately responsible for product design. They do understand this is a big change to the user experience. Thank you for keeping your honest feedback open and respectful.

Update Oct. 7, 2022

As this new experience rolls out to a greater number of Outlook users, many have expressed their concern about the effect this has on the leftmost UI components and Outlook's use of space. This feedback mirrors that found in other Microsoft forums and has resulted in one notable change. Starting with version 2210, you can make the Folder Pane even narrower than before, allowing you to redistribute some of the horizontal space to the Message List and/or Reading Pane.

Update Nov. 9, 2022

Version 2211 will introduce a temporary option to hide the new experience and return to the classic Outlook navigation bar. If you choose to opt out and see the prompt for feedback, please take a few moments to submit your reasons. Outlook may also invite you to re-evaluate the new experience when new apps or more app-related functionality is introduced in the future.

The new option can be accessed from by clicking the More Apps icon and then clicking Options.

This opens the Outlook Options, Advanced tab where you can uncheck Show Apps in Outlook, then restart Outlook to return to the classic navigation bar.

A change to the Outlook user interface

The location for accessing Outlook modules is being moved from the bottom to the left. The new location lets you find and use apps in addition to Outlook's core modules.

This update is a step towards a consistent experience across apps like Outlook, Teams, and Office.com. From the new location, you can switch apps and it creates room in the UI for more apps to integrate with Outlook. You can easily launch popular apps like To Do, Yammer, Bookings, Word, Excel, and PowerPoint without leaving Outlook, with more to come. Currently, only Microsoft apps such as Yammer, To Do and Bookings are available to users.

Details on the roll-out (key dates and builds)

Outlook users on Current Channel have been able to opt-in to try the new experience since March 2022. They could opt-in by enabling the Coming Soon toggle.

However, with Current Channel version 2207 released in September, this feature was turned on for 10% of Current Channel build users, with the number increasing over the following weeks/months. As the new experience rolls out to more users, it cannot be "turned off" or opted out of in order to return the navigation to the bottom.

Customizing the list of modules and apps

The Mail and Calendar modules are always on top. The remaining modules can be moved, pinned, or unpinned. The order you specify will roam across your Outlook clients. By default, M365 apps open within the Outlook frame, but you can choose to open them in a new window by selecting Pop Out App.

Click the More Apps icon to explore more applications.

Note In the future, More Apps will also include a new Store where you can install apps built using the updated Teams SDK as mentioned in Microsoft Teams apps designed for Microsoft 365 coming in Preview to Outlook and Office.com.

To disable the peek that appears when you hover over an Outlook module, right click on the module and uncheck Show the Peek on Hover.

Keyboard shortcuts

Keyboard shortcuts are aligned with the order in which they are displayed, from top to bottom. Since the Mail module is in the top-most position, its shortcut is Ctrl + 1. The second module (Calendar) is Ctrl + 2. This pattern is followed, even with your customizations. For example, if you choose to pin Folders and move it to the third position, its shortcut becomes Ctrl + 3.

Note Your app customization settings are locally stored in the following location:

C:\Users\<useralias>\AppData\Local\Microsoft\Outlook\HubAppCache\IdentityGUID_ADAL folder

Commonly asked questions

Why do I not see the feature in my Outlook?
Check to see if you have Coming Soon toggle turned off. It is also possible that you are on a channel which does not have the feature enabled.
Why is a particular app missing for me?
M365 apps are available based on user license. Please ensure you have the appropriate license enabled for the app.
Is this feature supported for Exchange on-premises mailboxes?
Yes, but only core Outlook modules, such as Calendar and People, are available.
Is there a centralized store for all apps?
Currently the apps are available based on user license. In the future, the apps built on the new Teams SDK will be in a single, centralized app store.
How do I disable an app for a user/tenant?
Currently, only a set of Microsoft apps are available in the app bar. Outlook will show/hide these based on whether the user is licensed for the service. Administrators can use the Microsoft 365 Admin Center (MAC) to assign/turn off the associated license for users in their organization – e.g., hide To Do by having it unassigned for a user.

Recommended SMIME algorithm settings for modern Outlook builds

Thomas_Noack — Thu, 14 Jul 2022 15:27:54 GMT

To take advantage of the best security available when using SMIME for email, you must configure Outlook to use modern algorithm settings. This post explains how ensure you are using these modern algorithms for encryption and digital signatures. This is important, considering that Windows and Outlook still allow you to use older and less secure algorithms for encryption and digital signatures.

The following registry values give you a good start for configuring a security profile using stronger algorithms, thus providing higher security for digitally signed and encrypted email messages using SMIME.

Furthermore, these values disable less secure algorithms, preventing their use in Outlook.

These registry keys need to be set before you configure the security profile. If a security profile has already been set up, make a note of the settings, then delete the security profile, restart Outlook, and create a new security profile.

To view and configure security settings, click the File menu, then click Options, Trust Center, click the Trust Center Settings button, then click Email Security, and then the Settings button.

To set the following higher security algorithms as the new defaults, use the registry settings below:

Encrypted email - AES 128 bit (2.16.840.1.101.3.4.1.2)
Digital signature - SHA 384 bit (2.16.840.1.101.3.4.2.2)

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Office\16.0\Outlook\Security]

"UseAlternateDefaultHashAlg"=dword:00000001

"DefaultHashOID"="2.16.840.1.101.3.4.2.2"

"UseAlternateDefaultEncryptionAlg"=dword:00000001

"DefaultEncryptionAlgOID"="2.16.840.1.101.3.4.1.2"

[HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Office\16.0\Outlook\Security\CNGAlgs\3DES]

"Flags"=dword:00000001

[HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Office\16.0\Outlook\Security\CNGAlgs\RC2]

"Flags"=dword:00000001

[HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Office\16.0\Outlook\Security\CNGAlgs\SHA1]

"Flags"=dword:00000001

The security profile should look like this:

These registry keys are supported in the following versions:

Outlook 2016 MSI with KB4486720 installed (November 3, 2020 Update)
https://support.microsoft.com/topic/november-3-2020-update-for-outlook-2016-kb4486720-bd780099-843a-7f80-ae88-c1b9fdc0abc9
Office 2019 VL + Retail
Office 2021 VL + Retail
Microsoft 365 Apps
(see About Microsoft 365 Apps )

How Outlook for Windows connected to Exchange Online utilizes Microsoft Search

Jason Creighton — Fri, 14 Jul 2023 16:03:18 GMT

Microsoft Search

In Microsoft 365, Microsoft Search returns search results based on the context of the application that you are searching from. When searching in Outlook, Microsoft Search is used to search email messages that are in your mailbox. There are plans for later builds to also query the Calendar, files, and other items within Outlook.

For general information on Microsoft Search, see Overview of Microsoft Search.

The evolution of Search in Outlook

It’s hard to imagine an Outlook without search. In its earliest versions, Outlook supported basic filters based on MAPI restrictions. Starting with Outlook 2007, Outlook has utilized Windows Desktop Search (WDS) to index Outlook Data (.pst) and Offline Outlook Data (.ost) files. These data files are normally stored on the local disk, as are the WDS search indexes. Although WDS provides excellent performance using the indexes on the local disk, mailbox sizes have increased while less mailbox data is synchronized to the local disk. This shift has resulted in a clear need for server- and service-powered search solutions.

This is where Microsoft Search comes into the picture. It fully indexes and searches content, while providing rich and intelligent search features that have become an industry norm. Throughout this journey, Outlook has evolved from local and MAPI-restriction searches, to server-based Exchange content indexing, to EWS/FAST search, and now to the most recent service-based iteration, Microsoft Search.

FAST Search continues to be used in Exchange Server 2016 and 2019 versions. For more information about FAST Search, see How Outlook 2016 utilizes Exchange Server 2016 FAST Search

Scenarios where Outlook uses Microsoft Search

This section is organized to help you determine which search solution is being used, based on a specific scenario. The Outlook product group is updating current versions of Outlook desktop, web, and mobile clients to migrate more and more scenarios to use Microsoft Search.

Note If Outlook cannot connect to Microsoft Search, an error message is displayed with a link to perform a local search.

The following tables list Outlook for Windows search scenarios, along with their current status and future plans to onboard them onto Microsoft Search.

Supported on Microsoft Search

Scenario	Details
Primary Mailbox - Cached Mode	Complete
Primary Mailbox - Online Mode (i.e., not Cached Mode)	Available in Monthly Channel builds >= 16.0.12716 Note By default, new Exchange email accounts are configured in Cached Exchange Mode. Online Mode is not related to Internet connection status.
[Explicitly Added] Shared Mailbox	Complete
All Mailboxes scoped search	Complete, available in builds >= 16.0.12716
Subfolder scoped search	Available in Monthly Channel builds >= 16.0.12920
Primary Calendar search	Complete
Online Archive	Available in Monthly Channel and Monthly Enterprise Channel builds >= 16.0.13519
KQL Terms	Partially migrated - From, To, CC, Subject, HasAttachments, IsRead, Importance, Kind, and Size use Microsoft Search Received as of build 16.0.14314 All other special KQL terms continue to rely on local search\MAPI restrictions Note: New date picker in Advanced Search will leverage Microsoft Search

Migration to Microsoft Search In Progress

The Current Channel (Preview) referenced in the following table was formerly called Monthly Channel (Targeted) or Insider Slow. For details on the Current Channel Preview release dates, see https://docs.microsoft.com/en-us/officeupdates/update-history-current-channel-preview.

Scenario	Details
Microsoft 365 auto-expanding archive	Available in Monthly Enterprise Channel builds >= 16.0.13519 Note Not supported with on-premises primary mailbox. In a hybrid deployment, the mailbox must be an online mailbox configured with a cloud-based archive mailbox.
[Automapped] Shared Mailbox	In progress - Not yet available
[Automapped] Delegate Access	In progress - Not yet available
[Explicitly Added] Delegate Access	In progress - Not yet available
Shared Folder	In progress - Not yet available
Shared Calendar	Not started - Local search uses Windows Search. Online search uses MAPI restrictions
Delegate Access Calendar	Not started - Local search uses Windows Search. Online search uses MAPI restrictions

Not planned for migration to Microsoft Search

Scenario	Details
Public Folder	No plans to migrate - Local search uses WDS. Online search uses MAPI restrictions.
All Outlook Items Search	No plans to migrate - Local search uses WDS. Online search uses MAPI restrictions.
Group Search	No plans to migrate - Local WDS search only.
Work Offline	No plans to migrate - By nature of the scenario, only local search is supported.

Set Outlook as default MailTo application

Cody_Matson — Fri, 12 Jun 2020 21:12:06 GMT

If you are an administrator and are responsible for the deployment and maintenance of Microsoft Office in your organization, it is almost certain that at some time you have been asked to customize Microsoft Outlook.

This post focuses on one specific configuration option that you can set by default: configuring Windows clients to use Outlook as the default MailTo email program.

Although individual users can manually set this option in Windows Settings | Choose a default app for each protocol, this assumes that the user is familiar with the setting. Otherwise, this can result in calls to the help desk.

Before Windows 8, you could control the handling of the MailTo protocol by deploying a single registry value or group policy, thus setting outlook.exe to Default:

HKEY_CLASSES_ROOT\mailto\shell\open\command

However, the above method does not work in Windows 8 and Windows 10. The default application for the MailTo protocol is now stored here:

HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\URLAssociations\MAILTO\UserChoice

Since Windows uses a hash to protect this new registry location, you cannot simply edit the values stored in that path. Instead, you must use an XML-based group policy to define the set of default apps.

Create your App Associations XML

Manually configure Default Apps in Windows Settings on your source PC
1. For MailTo, click Choose default apps by protocol then find MAILTO in the list. Set Outlook as the default app:

Once the defaults are set, use DISM to export these values to XML

From an administrator command prompt:

Dism /Online /Export-DefaultAppAssociations:"F:\AppAssociations.xml"

Note The XML will be based on the defaults set for the user account used when running DISM

Note For Outlook to be the default for opening MailTo links, you should see a line like this in the XML:

Deploy your App Associations XML via GPO

The name of the policy to use is Set a default associations configuration file and is found in the administration templates at this path:

Computer Configuration\Administrative Templates\Windows Components\File Explorer

Set this policy to Enabled
Specify the path to the app associations file that you previously created

Note This can be a local path or a network location that all clients can access

This policy should create the following key:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\System

String Value: DefaultAssociationsConfiguration

Data:\\ServerPath\AppAssociations.xml

Note This policy only works for domain joined clients

After this policy is in place, the default application associations are applied once the user logon occurs. The user should now see MailTo links open an Outlook email message.

ZeroConfigExchange - Automating the Creation of an Outlook Profile for Exchange Accounts

G_Cozier — Thu, 17 Oct 2019 20:45:52 GMT

Often we are asked if we can automate the creation or modification of new Outlook profiles, en-masse, for Exchange accounts... without user interaction. Typically, an Outlook profile (.prf) file, which is generated through the Office Customization Tool (OCT), can be used for most situations. However, there are two scenarios under which the use of .PRF files are not supported:

Exchange accounts - the .PRF file requires an Exchange server name to be hard-coded. This is normally acceptable for on-premises environments using Exchange 2010 and previous versions, but for Exchange 2013 and greater, along with for Exchange Online accounts, the server name contains a variable GUID that can change from time to time and from user to user.
Outlook 2016 - changes to how Exchange Autodiscover information is stored in parallel with an Outlook profile prevents the use of .PRF files to configure Exchange accounts in Outlook 2016. Outlook clients no longer connect to a server fully qualified domain name (FQDN) as they've done in all previous versions of Exchange. Using Autodiscover, Outlook finds a new connection point made up of the user's mailbox GUID + @ + the domain portion of the user's primary SMTP address.

While you can still use a PRF for your on-premises environments and Outlook 2013 or earlier versions, it is recommended that you use Autodiscover, which is supported for creating Outlook profiles in both on-premises and Exchange Online environments.

So, how can we automate the Outlook profile creation?

ZeroConfigExchange (ZCE)

ZeroConfigExchange (ZCE) can be used to create new profiles for users with minimal user interaction. That is, the user does not have to enter any configuration data... only data that every user should already know (account name and/or password). ZCE is a registry setting that tells Outlook to create a new profile using the SMTP address from Active Directory and to then leverage Autodiscover. It's important to note that there are no supported tools for modifying an Exchange Online account. Again, ZCE is used as a way to automatically configure an Outlook profile for one or many users with Exchange Online or Exchange on-premises accounts. However, the underlying mechanism used to gather configuration data for your connection to Exchange is Autodiscover.

Implementing ZCE

Implementing ZCE is easy. It can be added (through a login script) to the user's registry or as a group policy setting for all users. Here's how:

1. In the Windows Registry, navigate to the appropriate subkey for each version of Outlook that is in use:

For Outlook 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
As a policy: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\AutoDiscover
For Outlook 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\AutoDiscover
As a policy: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\Outlook\AutoDiscover
For Outlook 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\AutoDiscover
As a policy: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\Outlook\AutoDiscover

2. Once the key is created, right-click in the right pane and click New, click DWORD Value and type in “ZeroConfigExchange” (without the quotes) and then press ENTER.

3. Finally, right-click ZeroConfigExchange, click Modify and then in the Value data box, type 1, and then click OK.

Note If you choose to deploy the setting using a Group Policy Object (GPO), see Managing Group Policy ADMX Files Step-by-Step Guide on the Microsoft TechNet Web site. For more information about how to use group policy, see the FAQ: Group Policy on the Microsoft TechNet Web site. The Office 2016 Administrative Template files (ADMX/ADML) are available from the Download Center.

ZCE User Experience

ZCE can be used in a couple of scenarios, with each behaving differently. It can be used in an initial Outlook Deployment for automatic profile creation, or when Outlook profiles already exist and a change requires a new profile to be created, such as a change to the target server. In either case, the user is not required to enter --or even know-- configuration details.

Initial Outlook Deployment

An initial Outlook deployment occurs when Microsoft Office or Microsoft Outlook is installed on the user’s workstation for the very first time. This means that no Outlook Profiles currently exist on the PC. As part of the deployment, ZCE could be configured via the Office Customization Tool (OCT). In this case, Outlook starts and the Outlook profile is automatically created during Outlook's first-run process. In a perfect case, there are no prompts. However, there may be a prompt for a username and password, depending on the Exchange Online configuration. Again, the user will not need to know nor need to enter any configuration details.

When Outlook Profiles Already Exist

This scenario would be necessary in cases where users need new profiles creates after having pre-existing profiles on the machine. This scenario requires additional registry keys be created (or pushed out to the user via GPO).

Note: Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.

For Outlook 2013/2016/2019:

Exit Outlook.
Start Registry Editor. From the Start menu, type regedit.exe in the search box, and then press Enter.
Deploy ZeroConfigExchange key as mentioned above.
In Registry Editor, locate and then click the following registry subkey: HKEY_CURRENT_USER\Software\Microsoft\Office\XX.0\Outlook (XX.0 will represent the version of Outlook version – 16.0 = 2016/2019, 15.0 = 2013).
Select DefaultProfile in the right pane and click Modify.
Change the value data to the new profile name that you want to create. Make sure that it is not the same as any of the old profiles stored on the machine.
Click OK.
Browse to HKEY_CURRENT_USER\Software\Microsoft\Office\XX.0\Outlook\Profiles (XX.0 will represent the version of Outlook version – 16.0 = 2016, 15.0 = 2013).
Right click Profiles and select New > Key.
Replace the value of the new key with the name of the profile that you provided in Step 6.
Press Enter.
Close Regedit.

Note: For Outlook 2010, the location of the keys that need to be changed are located under HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles.

It might be best to run gpupdate /force and reboot the machine to make sure that the settings stick and aren't overwritten by any existing polices. After the reboot, I’d recommend setting Outlook to prompt for profile to ensure that the new profile is being created at launch. Outlook should display the new profile created as the main profile for login at the splash screen if set to prompt for profile, otherwise if not set then Outlook should load directly into the new profile at startup.

This forces Outlook to create the new profile and the ZeroConfigExchange process to populate it with the additional profile data. If these registry settings are not set or created, Outlook uses the current default profile and will bypass ZCE. As mentioned earlier, there may be minimal interactions with the user depending on your environment. Again, in a perfect case, there are no prompts. However, there may be a prompt for a username and password, depending on your Exchange Online configuration.That's it for ZCE. Create new profiles with minimal user interaction. Plain and simple.

Conflicting permission sets when working with shared or delegated folders in Outlook

abdias_ruiz — Mon, 18 Jul 2022 18:12:12 GMT

Outlook allows users to share folders so that others can interact with items in those folders. Additionally, a user can be configured as an Outlook Delegate, allowing him or her to manage specific tasks on your behalf, such as meeting related tasks. If another user grants you folder permissions (or makes you a delegate) and you use Outlook to perform actions on that user's shared items, Outlook performs these actions using a specific permission set. However, there are a couple of different ways that you can be granted access to a user's folders. Each of these ways can create a different permission set, which can later result in conflicts.

Important Outlook for Microsoft 365 introduced Calendar sharing improvements that are based on the REST protocol. A shared calendar that syncs using the improved calendar sharing model is not susceptible to the limitation described in this blog post. To determine if you are using the new Calendar sharing model or if your organization supports it, see the Microsoft Support articles Calendar sharing in Microsoft 365 and Outlook calendar sharing updates.

The diagram below shows how Outlook can be exposed to conflicting permission sets. Let's start with the following facts:

Permission set X is created when the Exchange Server Administrator grants you FullAccess permission to Allison's mailbox.
Permission set Y is created when Allison grants you explicit folder permissions by using Microsoft Outlook. Allison can do this in one of two ways:
- Grant you individual folder permissions by right-clicking on a folder and selecting Permissions.
- Configure you as an Outlook Delegate to specific Outlook folders, such as the Calendar.

When you use Outlook to work with Allison's shared items, Outlook may initially use one specific permission set (this is Permission set Y in the diagram below). As you continue using Outlook to work with Allison's items, a particular function may be blocked within the existing context (again Permission set Y). In this case, some expected functionality may not be available. However, it is important to note that the unexpected behavior will not be consistent, nor can it be clearly defined here, because the initial context used by Outlook can differ depending on how Allison's mailbox or shared items are first accessed by Outlook.

In the diagram, you see that the elevated permissions necessary to perform tasks on Allison's other folders are not available. This occurs because Outlook is not designed to consistently work with two or more permission sets.

In some cases, Microsoft documentation points this limitation out. For example, some of the issues that can occur due to conflicting permission sets are listed in the following Microsoft Knowledge Base article:

981245 Issues that can occur when you add multiple Exchange accounts in the same Outlook 2010 profile

The bottom line: the easiest way to remember the limitation (and to avoid it) is by granting permissions using only one application: either Microsoft Outlook or Microsoft Exchange Server.

Note for Office 365 mailbox users: If you and the person sharing their calendar with you both have Exchange Online mailboxes on Office 365, you may be able to take advantage of a new shared calendar experience. The new calendar sharing model makes significant improvements to the user experience. For more information about the new model, see the following Office help article:

Calendar Sharing in Office 365

Which application should you use to give permissions to your items?

Since a user should only use one of two methods (Outlook or Exchange) to share their folders or entire mailbox, the following table will help you choose. The table lists some of the benefits and functionality that are available with each method.

	Exchange FullAccess	Outlook Delegate or Shared Folder
Shared mailbox appears in the Outlook Navigation Pane	Automatically, if both of the following are true: a. Exchange FullAccess permission is granted with AutoMapping enabled on Exchange Server 2010 SP1 or later. b. You are using Microsoft Outlook 2010 or newer. Otherwise, you can manually add the shared mailbox as a second account using File \| Account Settings.	Not if you are only given permission to a specific folder or are only granted Delegate access. However, there is an exception. The user can grant you at least View permissions to their top level folder. Then, you add the shared mailbox to Outlook by using the Open these additional mailboxes option. If the user wishes to grant you access to their other non-default folders, they can set folder permissions on each individual folder.
Receive meeting invitations on other's behalf	No	Yes - if you are configured as a Delegate. No - if you only have folder permissions.
Able to view private items in shared mailbox	No	Yes, if you are configured as a Delegate and with the option "Delegate can see my private items". Note To view private items in other folders such as contacts or email folders, you must also be granted Reviewer permission to the Calendar.
Able to open shared mailbox in OWA	Yes	No
Effect on Offline Outlook Data (.ost) file size	One .ost file is created. It contains the contents of both your mailbox and of the shared mailbox.	Reduced size since only specific folders are being shared and cached (the additional shared folders are cached in the same .ost that is associated with the delegate's Outlook profile).
Other considerations	Not optimal as it requires maintaining permissions on both the Exchange Server (FullAccess) and Outlook client delegate/folder) permissions. Although the Exchange administrator can control this set of permissions, the administrator has no control over Outlook clients. Therefore, if a client chooses to configure delegate/folder permissions, they can enter an unsupported state. Additionally, the shared mailbox is fully exposed to any unexpected actions performed by the secondary user (or by any of their add-ins or devices).	This is the recommended option, as it limits the effect that other users' add-ins or devices can have on the owner's mailbox. Additionally, it prevents Outlook clients from being configured in an unsupported state.

Solution: Avoid the conflicts

The manager, delegate, and possibly the Exchange admin must consider the details in the above table and decide which changes to make to ensure an optimal configuration. For example, the necessary changes may involve one of the following solutions:

Option 1

Action - If the delegate needs to manage all of the manager's folders, then they should maintain Full Access permissions. However, the manager needs to remove the delegate using the Outlook client. To do this, the manager clicks on File, then clicks Account Settings, and then clicks Delegate Access to remove the delegate.

Result - The delegate will no longer receive the manager's meeting invitations in their own mailbox. The delegate must open the manager's Inbox to respond to their meeting invitations.

Option 2

Action - The Exchange admin uses either the Exchange Admin Center or the Exchange Online PowerShell to remove Full Access permissions:

‣ they open the Exchange Admin Center and then open the manager mailbox. In the Mailbox permissions tab, they remove the delegate from Full Access.

‣ or the admin runs the Exchange Online PowerShell cmdlet:

Remove-Mailboxpermission –identity ManagerAlias –user DelegateAlias –Accessrights FullAccess

Result - The delegate no longer sees the manager's mailbox in their Outlook profile nor in OWA. The manager does not need to make any changes in the Delegate Access dialog in Outlook, unless they now want to also grant access to the Inbox. The delegate continues to receive meeting requests and responses based on the Delegate Access settings.

Additional resources

One delegate can manage multiple mailboxes. However, any given mailbox should have a limited number of delegates. Additionally, only one delegate with Editor permission is recommended. See the following Office Help article for more information:

Best practices when using the Outlook Calendar

Exchange administrators may be interested in the following Microsoft Docs article, which explains how to disabling Auto Mapping:

Disable Outlook Auto-Mapping with Full Access Mailboxes

32-bit Outlook interface elements unexpectedly render in black, white, or blank

MSFTsfellman — Sat, 08 Feb 2020 05:14:11 GMT

Updated: May 1, 2018 and June 13, 2018 and October 15, 2019

Microsoft has worked across multiple product engineering teams to provide additional fixes for Outlook rendering issue for users in VDI scenarios; these changes also improve performance on physical machines. This update enumerates those changes.

Windows

The major update comes from our Windows team. Windows Advanced Rasterization Platform (WARP) fixes have shipped for currently supported versions including 1709 and 1803; patch as applicable:

No special patching is required for RS5 and higher; the WARP changes are included already.

Office

We have rolled up a few more minor updates from the Outlook and Airspace teams.

Office ProPlus (OPP) users got changes in Monthly Channel version 1907.

OPP Semi-Annual Channel (SAC) received changes for rendering issues effective January, 2020, with Version 1908.

MSI (Perpetual) builds of Office requires the following patches

Outlook.exe - https://support.microsoft.com/en-gb/help/4475553/security-update-for-outlook-2016-august-13-2019
mso40UIwin32client.dll - https://support.microsoft.com/en-gb/help/4464588/august-6-2019-update-for-office-2016-kb4464588

Other Notes:

This recent work will not get backported to 2013 Office since that product is now in extended support – no new features or fixes ship there except security updates.
For impacted Outlook 2013 users, give them the WARP fix for their specific Windows version and enable Outlook LAA. Remember that LAA for Outlook 2013 requires both a patch and a registry key: https://support.microsoft.com/en-us/help/4022148/update-to-enable-large-address-aware-for-the-32-bit-version-of-outlook. If those options don’t work, they can try x64 Office or they can update to Office 2016 MSI or Office ProPlus (OPP).
If you apply all patches and still see these rendering issues, be sure to update all your add-ins to the latest available from each add-in vendor.

The continued work of the Airspace, Outlook, and Word development teams resulted in Office updates and optimizations that address the remaining 32-bit Outlook rendering issues. This update provides details on two areas of particular interest: Airspace and Large Address Aware (LAA) functionality.

Airspace

Changes to Airspace were mostly completed in the November 2017 updates for Office 2013 and Office 2016. As you likely know, Office updates are cumulative, thus we recommend patching with the latest available updates for Office. A significant finding to share is related to hardware graphics acceleration and virtualization. Some customer feedback indicates many popular virtualization solutions do not support hardware graphics acceleration. Since enabling hardware graphics acceleration is required to fully benefit from the Airspace improvements, if you find the virtual solution that you are administering doesn’t support hardware graphics acceleration, please reach out to the software vendor to request support.

Outlook Large Address Aware Feature

As mentioned in the original post below, Microsoft was working on enabling a "large address aware" (LAA) Outlook. Due to the significant memory handling changes involved with LAA, Outlook development elected to follow the standard channel release model for the new feature in Office 2016 ProPlus. The Outlook LAA feature has made its way into both the Monthly Channel and the Semi-Annual Targeted (SAT) channel of Office 2016 ProPlus as of this writing and ~~should port~~ was ported into the Semi-Annual (SA) channel on May 8, 2018 ~~in summer 2018~~. LAA Outlook is also included starting with these MSI updates:

Initial reports indicate full resolution when both Office is updated (to include the Airspace changes) and an Outlook build that includes the LAA feature is used. Although others have indicated the rendering problems continue, they occur with a low frequency, hardly impacting their help desks. Still others –mostly users of memory-heavy Outlook add-ins– have chosen the 64-bit Office path to resolve the rendering issues. For some background on LAA, you can read the Office marketing team's article on the subject.

Original post...

Starting in mid-2016, some Outlook 2013 and Outlook 2016 users began noticing rendering issues and posting reports in our forums and communities. Then, in late 2016, similar reports started filtering into our support teams. The symptoms have included:

Buttons on the Outlook ribbon failing to paint properly
Email messages displaying either blank or black in the Reading Pane
The Navigation Pane failing to draw all folders properly
Various rectangles appearing in the Outlook user interface (UI)

The frequency of the problem has varied by user. Some have seen drawing failures once a week, while others two, three, or more times per day. These problems can affect all Office deployment technologies, including perpetual (also called MSI) and subscription (also known as Click-to-Run or C2R for short). In this post, we describe the architecture of the Office/Outlook rendering model. Additionally, we share steps to proactively mitigate the rendering issues. And lastly, we give you a peek inside the continued development efforts aimed at resolving these problems.

Background

Outlook is the main messaging application within the Office suite. Outlook uses shared Microsoft Office (MSO) code to perform many functions. Examples include Outlook's use of Microsoft Word for spell checking and HTML rendering and Outlook's use of shared Office ADAL code to perform Modern Authentication related operations. Office 2013 introduced a new rendering engine called Airspace to all the Office applications. Airspace's promise was to better leverage the hardware based graphics from DirectX in Windows 8 to enable new design experiences like animations and layered composition. Outlook continues to use Word and other shared office code like Airspace in the 2016 version. The initial release of Airspace as the Office/Outlook rendering engine came at a time when many devices did not have sufficient video hardware to accommodate the new rendering feature set. As a result, many users and firms forcibly deployed policies to disable hardware graphics acceleration, despite the fact that Office code was designed to turn the feature off if the hardware did not support it. Such policies still exist in many enterprises, although in most cases today, they could safely be removed (except for a few, very specific instances).

Rendering Issue Specifics

The players in the various iterations of the Outlook rendering problem are:

Outlook (our hero)
AirSpace (Office rendering engine)
Word (key for many Outlook functions)
Windows 32-bit application virtual address space composition (the law)

The primary cause of the rendering failure is memory pressure within the 32-bit Outlook process. Technically speaking, Outlook runs out of space for memory allocations within the process' virtual address space, resulting in rendering failures. This memory pressure comes in two forms, both viewable with the VMMAP tool:

A smaller than required available contiguous memory block (example: a texture requires a 128 kb memory block to render, but the smallest contiguous block available is 96 kb)
Low virtual memory available to the Outlook process (less than 250 MB free of the 2 GB total that Windows gives to all 32-bit processes)

Interested readers can dive deeper with VMMAP.

High resolution monitors
Outlook content spread across multiple monitors
Touch screens used to scroll through email and other messages within the UI (because of the bandwidth required to render screen content)
Use of unneeded or excessive COM add-ins
Large numbers of PST files added in the Outlook profile
DirectX failures due to older drivers
Dock/undock scenarios where resolution changes suddenly
Heavy use workflows (keeping many messages open, keeping many attachments open, crafting email with lots of graphic effects from WordArt, etc...)

The rendering issue seems to surface most frequently on high-resolution monitors. Older monitors rendered in 1600x1200 pixels. However, newer monitors may render at 3840x2160, or four times more pixels. The spike in 2016 for support cases with the rendering issues correlated to the increased adoption of higher-end hardware. Drawing the same UI surface for Outlook requires more pixels on the higher-res screens, and more pixels translate to more memory required, hence the quicker exhaustion of memory resources dedicated to the Outlook process. In simple terms, a full screen Outlook window that required 8 MB on an older monitor now requires 32 MB on a 4K display. Factor in lots of redraws and you understand how memory is quickly exhausted, leading to rendering failures. And a final note on high-res monitors: there is no vendor bias involved... the resolution on Microsoft Surface is similar to devices from Lenovo, Dell, or other hardware manufacturers, each vulnerable to 32-bit Outlook rendering pains.

Mitigation

The best mitigation for these issues -without question- is to move to 64-bit Microsoft Office. Windows provides four thousand times the addressable user-mode memory to 64-bit processes than it does to 32-bit processes. More memory is the best way to fight memory depletion issues. Note Some may get stuck on this recommendation, mostly due to add-in compatibility concerns and other concerns. Maybe your add-in vendor provides a 32-bit version of the add-in without an option for a 64-bit version. If this is your situation, we advise that you open a support case with your add-in vendor and insist on a 64-bit version of their product. The 32-bit limitation is immutable, hardware continues to get better, and extending Outlook with COM Add-ins is commonplace. 32-bit is not the future of desktop computing. Once you verify that you have rendering issues caused by a low memory state within the Outlook process, determined on your own or by working in tandem with Microsoft Support, there are steps you should take immediately to start mitigation:

Patch to the latest available versions of Outlook, Word, and MSO
Ensure hardware graphics acceleration is enabled:
- Start any Office application
- Click the File tab, then Options
- Then click the Advanced group
- In the Display section, ensure that the Disable hardware graphics acceleration check box is cleared, as shown here:
Update video drivers to the latest provided by the video card manufacturer

For impacted users that cannot go to 64-bit Office for one reason or another, and for whom the previous steps do not fully resolve the rendering problems, there are other options to relieve memory pressure. To this end, some or all the following may help:

Restart Outlook regularly
Change DPI settings to greater than 200% on high-res monitors
Modify your Outlook workflow
- Keep fewer Outlook windows/messages open
- Disable or remove unneeded Outlook COM Add-ins
- Remove PST files from the profile when not used
- Avoid touch-scrolling through messages
- Avoid multiple monitor use with Outlook
For extreme cases:
- Use OWA
- Use Office 2010/Outlook 2010 (works past the problem since Office 2013 introduced Airspace)
- Update to Office 2016/Outlook 2016 (where we first implement product changes)

Roadmap

During the first eight months of 2017, the Airspace, Outlook, and Word development teams shipped over twenty code changes and optimizations into Office to reduce the frequency and severity of the 32-bit Outlook rendering issues. These changes address the glaring problems found during investigations of this past year. The bulk of this work shipped in June 2017, and further coding and testing continue through the time of this writing in order to eliminate other problems that we've isolated. Today, we are researching more complex rendering scenarios like multi-mon and docking/undocking scenarios for potential solutions. We are working on enabling a "large address aware" (LAA) Outlook, a step taken in 2016 by the Excel>Office Insider Fast by Outlook development. LAA promises to increase available process memory on 64-bit Windows to 4 GB, or a factor of one hundred percent. While the LAA increase is less than that of moving to a native 64-bit Office deployment, the important note is that Microsoft is looking at every possible angle to improve Outlook rendering. So far, all fixes taken are present in MSI builds of Office 2013 and 2016. Other development work outside the scope of this blog is happening too. Some of these ideas may only prove safe in Evergreen builds of Office 2016. Time will tell. Going forward, we plan to ship more fixes as we isolate problems. Due to the complexity of these issues and the number of teams involved, we expect that related changes will ship not all at once, but rather in a phased manner over the coming months. This approach mandates that our customers keep current on Office patch levels. And of course, if you have questions, we invite you to open a support ticket and work with our support teams to assist.

How Outlook 2016 utilizes Exchange Server 2016 FAST Search

abdias_ruiz — Tue, 27 Sep 2022 16:10:32 GMT

FAST Search

The term FAST Search may not be entirely new to you if you managed SharePoint sites anytime during the last decade. With Microsoft Exchange Server 2016, the FAST search architecture is introduced to Exchange. With FAST search, various new features are made available to Exchange 2016 mailbox users, including Search suggestions and People suggestions. These suggestions are dynamically computed based on your previous searches and the names of people that you frequently communicate with. The new feature set is readily available when using Outlook on the Web to connect to a mailbox on Exchange Server 2016 or Exchange Online.* Additionally, the newer Outlook 2016 desktop client also takes advantage of the new FAST search when connecting to these same mailboxes.

* Note Exchange Online on Microsoft 365 is migrating search features from FAST to Microsoft Search. However, on-premises Exchange Server will continue to use FAST search. For more information about the migration of Exchange Online search features to Microsoft Search, see How Outlook for Windows connected to Exchange Online utilizes Microsoft Search.

The evolution of Search in Outlook

As far back as in Outlook 2007, Outlook has utilized Windows Desktop Search (WDS) to index Outlook Data (.pst) and Offline Outlook Data (.ost) files. These indexes are created on the local disk. At the same time, Outlook uses the same WDS architecture to search these local indexes when you initiate a search. The use of WDS in Outlook is sometimes referred to as Instant Search.

Let us focus strictly on searching Exchange mailbox content... Exchange content is indexed by WDS when Outlook is configured to connect to the Exchange mailbox using Cached Exchange Mode. When an Exchange email account is in Cached Exchange Mode, the mailbox contents are synchronized to the local .ost file. It is this local file that is indexed by WDS. WDS does not index the mailbox store directly. Why am I still talking about WDS? Because it is still relevant, even when using the latest and greatest versions of Outlook and Exchange.

Search in Outlook 2016 and later versions

In Cached Exchange Mode, Outlook 2016, Outlook 2019, and Outlook for Office 365 still query WDS desktop search indexes... and they query Exchange 2016 and Exchange 2019 using FAST Search.

Assuming FAST Search is not disabled by policy, Outlook initially submits a query to Exchange on-premises using FAST Search. If FAST Search results are returned in a timely manner (about 5 seconds), these are displayed. But, if the FAST Search timeout is reached before a server response, then a message indicating that We're having trouble fetching results from the server..., along with the link "Let's look on your computer instead." If you click this link, then WDS search results are displayed.

Note Outlook also assesses the performance of the network connection and if it determines there is latency, it may default to displaying WDS search results.

But wait, there's more! Some search scopes set search criteria that cannot be processed by FAST. If you set the scope to All Outlook Items, Subfolders, or All Mailboxes Outlook defaults to WDS results. The search scope is set next to the Search text box, as shown here:

Additionally, if you type search criteria that is not supported by FAST, Outlook returns WDS results (of course, assuming WDS supports the criteria). For example, Outlook supports the use of natural language queries, such as received:this year. However, Outlook FAST search does not. Therefore, if you submit received:this year, Outlook automatically displays WDS search results. To use FAST search for a similar query, you would need to submit the following criteria: received>12/31/2016.

To recap, Outlook uses FAST search and/or returns results using FAST, except if any one of the following conditions are true:

You are connected to a mailbox on Exchange Server 2013 or earlier
Outlook is connected to the mailbox in online mode
The FAST search feature is disabled via policy or local user registry setting (more on administering the feature below)
The FAST search query results are not returned in a timely manner (about 5 seconds)
Outlook assesses the performance of the network connection and determines there is latency
You are searching a secondary mailbox (there's an exception to this exception, as explained later)
The search scope is set to All Outlook Items, Subfolders, or All Mailboxes
The search criteria are not supported by FAST search

Am I seeing WDS or FAST results?

To determine which results Outlook is displaying, you can focus on some small user interfaces cues.

If the results displayed are those generated by FAST, the bottom of your message list will display the following cue:

If there are more than 75 results from FAST, the bottom of your message list may display the following message until reaching the service or client limit, whichever is smaller:

As mentioned earlier, if the service times out or is unavailable, the message list will display the link “Let’s look on your computer instead.”

If you click Let’s look on your computer instead, the results displayed are those generated by WDS. Of course, this is assuming that your local copy of the .ost cache contains items that match your serach criteria. The items that you are searching for may not be locally cached if a limited time window is specified for the Mail to keep offline setting. When this occurs, no local WDS results are returned, but you are given the option to check the Exchange mailbox by clicking Find more on the server:

Just as earlier Outlook 2016 client versions did, clicking More sends a non-FAST query to Exchange. This is because the client has already determined that FAST search to the service is not available… no need to go back and try that again.

And yes, Exchange Server 2016 supports both FAST and legacy Exchange Search functionality. The latter is still required for backward compatibility with Outlook 2013 and earlier versions.

Secondary mailboxes

When Outlook 2016 released, the plan was to only support FAST search on your primary mailbox. However, starting in the Fall of 2017, Microsoft 365 Apps (formerly known as Office 365 ProPlus) in Current Channel and Enterprise Channels, and the latest Office 2019 version, now fully support FAST Search for any Exchange email accounts added through File | Account Settings (also known as MultiEx or multiple Exchange accounts). This does not apply to Outlook 2016 installed with the Office 2016 suite that uses Windows Installer (MSI) installation technology.

If you are limited to using an older build of Outlook 2016 or one installed using the MSI installation technology, searching in a MultiEx mailbox may submit the FAST query in the context of the logged on user (you). This causes the search results to be pulled from your own mailbox, not the secondary mailbox that currently has the focus in your Outlook client. If you are unable to upgrade your Outlook 2016 client to the November 2017 Monthly Channel Build, you can temporarily work around this limitation by using one of the following options:

Change the search scope to All Outlook Items, Subfolders, or All Mailboxes
Disable Outlook 2016's use of FAST search via policy or local user registry setting (see the next section)

Note Other types of secondary stores, such as those added via Open these additional mailboxes or those that are automatically configured via AutoMapping, are still limited to WDS.

Number of results returned

Currently, the service limits the results to 1000 results. However, Outlook can further limit the results to 250 if the File, Options, Search group, Improve search speed by limiting the number of results shown checkbox is enabled.

Administer FAST Search in Outlook

To disable FAST search (server assisted search) and revert back to using WDS, an administrator can apply a group policy or implement the DisableServerAssistedSearch and DisableServerAssistedSuggestions user registry values. These are documented in the following table, along with other registry values to allow you to control additional FAST search functionality.

Note The 16.0 registry subkey name is valid for both Outlook 2016 and Outlook 2019.

Disable Server Assisted Search	Group Policy registry path: HKEY_CURRENT_USER\software\policies\Microsoft\office\16.0\outlook\search DWORD: DisableServerAssistedSearch OCT registry path: HKEY_CURRENT_USER\software\microsoft\office\16.0\outlook\search DWORD DisableServerAssistedSearch	Disables Outlook from requesting and using Search results from Exchange for cached and non-cached mailbox items. Instead, it will use search results from Windows search service. Set to 1 to enforce.
Disable Server Assisted Suggestions	Group Policy registry path: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\search DWORD: DisableServerAssistedSuggestions OCT registry path: HKEY_CURRENT_USER\software\microsoft\office\16.0\outlook\search DWORD: DisableServerAssistedSuggestions	Disables Outlook from requesting search suggestions from Exchange. Set to 1 to enforce.
Default Server Latency Limit	Group Policy registry path: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\search DWORD: DefaultServerLatencyLimit OCT registry path: HKEY_CURRENT_USER\software\microsoft\office\16.0\outlook\search DWORD: DefaultServerLatencyLimit	If the connection to Exchange is slower than DefaultServerLatencyLimit in milliseconds, then do not issue an Exchange Server Assisted search (will only use local search).
Server Assisted Search Timeout	Group Policy registry path: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\search DWORD: ServerAssistedSearchTimeout OCT registry path: HKEY_CURRENT_USER\software\microsoft\office\16.0\outlook\search DWORD: ServerAssistedSearchTimeout	Timeout in milliseconds that Outlook should wait for Exchange to provide search results before falling back to use local search.
Search Suggestion Keyword Max Display	Group Policy registry path: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\search DWORD: SearchSuggestionKeywordMaxDisplay OCT registry path: HKEY_CURRENT_USER\software\microsoft\office\16.0\outlook\search DWORD: SearchSuggestionKeywordMaxDisplay	Maximum number of keyword suggestions displayed in Search textbox.
Search Suggestion People Max Display	Group Policy registry path: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\search DWORD: SearchSuggestionPeopleMaxDisplay OCT registry path: HKEY_CURRENT_USER\software\microsoft\office\16.0\outlook\ search DWORD: SearchSuggestionPeopleMaxDisplay	Maximum number of people suggestions displayed in Search textbox.
Search Suggestion Total Max Display	Group Policy registry path: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\search DWORD: SearchSuggestionTotalMaxDisplay OCT registry path: HKEY_CURRENT_USER\software\microsoft\office\16.0\outlook\search DWORD: SearchSuggestionTotalMaxDisplay	Maximum total number of suggestions displayed in Search textbox.
Wordwheel Time Out Exchange Search	Group Policy registry path: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\search DWORD: WordwheelTimeOutExchangeSearch OCT registry path: HKEY_CURRENT_USER\software\microsoft\office\16.0\outlook\search DWORD: WordwheelTimeOutExchangeSearch	The number of milliseconds that Outlook will wait after text changes in the Search textbox before executing a Search using the Instant Search (FAST) API.
Search Suggestion Time Out	Group Policy registry path: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\search DWORD: SearchSuggestionTimeOut OCT registry path: HKEY_CURRENT_USER\software\microsoft\office\16.0\outlook\search DWORD: SearchSuggestionTimeOut	The number of milliseconds that Outlook will wait after text changes in the Search textbox before issuing a query to FAST for suggestions.

Special thanks to Paul Slaathaug for reminding me to get this blog wrapped up and for providing additional topics to cover.