rss.livelink.threads-in-node

Will these commands fix our phantom meetings issue?

RyanSteele-CoV — Fri, 24 Apr 2026 16:04:49 GMT

I opened a ticket with Microsoft Support for an issue we are facing where "phantom" meetings are appearing in at least two of our meeting room calendars. The subject of the meeting says "Private appointment" and the lock icon appears at the bottom, and when you click on any of them they disappear from the calendar, only to re-appear when you navigate away and come back. They appear in Classic Outlook, New Outlook and Outlook for the web.

The support rep is telling me to run these commands on the room mailbox to "reset the room mailbox availability cache":

Set-CalendarProcessing -Identity <roommailboxupn> -RemoveOldMeetingMessages $true Set-CalendarProcessing -Identity <roommailboxupn> -AutomateProcessing AutoAccept

But if I run Get-CalendarProcessing, it confirms that these are the existing settings already:

Get-CalendarProcessing -Identity <roommailboxupn> | fl RemoveOldMeetingMessages,AutomateProcessing RemoveOldMeetingMessages : True AutomateProcessing : AutoAccept

This can't possibly do anything, right? I should ask my CSAM to open a GetHelp on this case, right?

Does anyone know how to actually fix this issue?

Disabling Calendar Repair Assistant on mailboxes in Exchange Onprem 2019

PoorMens_Bravo — Fri, 24 Apr 2026 04:33:10 GMT

Hi,

We are in Exchange Hybrid setup were some mailboxes are in cloud and onprem. Recently, there were some issues with Calendar events were recipients weren't notified of any updates for the events, sometimes the updated event would have been cancelled by recipient and the recipient didn't even know that they received update and it was automatically cancelled by them....

This was a normal situation for EAs for their executive calendar events

When raised a ticket with Microsoft on this issue, Microsoft collected CDL logs and found that CRA was kicking in each time when there was an update and was reverting the updated meeting request to the previous cancellation and as we know this is not a bug, this is just how the CRA works...So, Microsoft is like CRA is a legacy feature with limited applicability and functionality in the current exchange environment and hence has asked to disable-CRA in On-prem exchange as this will not affect normal calendar usage for users.

I had disabled for 5 users and they have reverted that they are not seeing any issues post disabling CRA. so before gunning down on all mailboxes I wanted to take a second opinion on whether is it safe to disable CRA for alll mailboxes in Exchange Onprem

Modernizing DNS Security for Exchange Online Mail Flow

The_Exchange_Team — Thu, 23 Apr 2026 21:00:39 GMT

The Domain Name System (DNS) protocol is used by clients to find mail servers over the internet. DNS is unencrypted and unauthenticated by default, making it vulnerable to spoofing, tampering, and adversary‑in‑the‑middle attacks. As threat actors increasingly target the foundational layers of email delivery, modern DNS security protocols have become essential to protecting organizations.

To address these gaps, Exchange Online has invested heavily in modern, standards‑based DNS security – including DNSSEC, SMTP DANE, and MTA‑STS – to ensure mail is delivered over validated, encrypted, and tamper‑resistant channels by default wherever possible.

In this post, we will provide updates on these efforts and discuss upcoming plans to keep raising the email security bar.

DNSSEC Enablement Wizard for Exchange Online

To simplify adoption of SMTP DANE with DNSSEC, in Q3 of calendar year 2026 we’re releasing a DNSSEC Enablement Wizard in the Exchange Admin Center. This guided workflow:

Validates DNS prerequisites
Provisions the customer-specific DNSSEC‑capable mail flow endpoint
Reduces configuration risk during MX transition
Prepares the domain for SMTP DANE adoption

For customers who wish to fully enforce SMTP DANE with DNSSEC, PowerShell will remain the option for enabling SMTP DANE once DNSSEC-enablement is complete as per Set up inbound SMTP DANE with DNSSEC.

Control Outbound SMTP DANE & MTA‑STS Validation on Connectors

With rollout started in late Feb 2026, we introduced a new capability that gives admins explicit control over SMTP DANE and MTA‑STS validation behavior for messages sent over outbound connectors.

The MtaStsMode and SmtpDaneMode parameters on New/Set/Get-OutboundConnector lets organizations choose how strictly Exchange Online enforces these security protocols on a per‑connector basis:

Opportunistic (default): Exchange Online attempts SMTP DANE and/or MTA‑STS validation but still delivers mail if the destination doesn’t support them.
None: which applies to both MTA-STS and SMTP DANE and disables the validation entirely, therefore reducing the security of emails sent over that connector by removing MTA-STS and/or SMTP DANE protections designed to prevent downgrade attacks and spoofed MX redirection.
Mandatory (SMTP DANE only): Enforces full SMTP DANE with DNSSEC validation and queues (then rejects) mail if validation fails or destination domain doesn’t support SMTP DANE with DNSSEC by end of queuing period.

This outbound connector capability makes it easier for customers to adopt stronger DNS‑based protections incrementally while maintaining compatibility with partner ecosystems.

What happened to auto-provisioning of DNSSEC-enabled mail flow records (A/AAA)?

Due to internal infrastructure projects, we had to delay this DNS provisioning change until second half of calendar year 2026. Gradually switching provisioning of all A records for new Accepted Domains into the new subdomains under mx.microsoft is still a priority for us, but making infrastructure changes is complex. Significant challenges have required us to re-order the work necessary to complete this change while maintaining service health and reliability.

Original announcement: Implementing Inbound SMTP DANE with DNSSEC for Exchange Online Mail Flow | Microsoft Community Hub.

Are there any planned updates to mail.protection.outlook.com?

Currently, there are no plans to enable DNSSEC on the mail flow domain mail.protection.outlook.com. Customers who require DNSSEC for inbound mail will continue to need to transition the DNSSEC-capable dedicated subdomains within mx.microsoft. As MX changes can be operationally sensitive, we built the DNSSEC Enablement Wizard to ease the friction of this change.

In early third quarter of 2026, mail.protection.outlook.com will receive TCP and EDNS support. This modernization improves reliability and enables future security enhancements at cloud scale.

Raising the Security Bar – Together

Across these investments, our goal is simple: make strong email security the default, without introducing additional operational complexity or overhead. DNSSEC, SMTP DANE, and MTA‑STS directly address long‑standing weaknesses in the global email ecosystem, and Exchange Online is committed to leading the industry in deploying these foundational protections at scale.

By modernizing our DNS infrastructure, providing safer tooling for domain transitions, and giving customers finer control over protocol enforcement, we’re continuing to raise the security bar for all Exchange Online customers—and making it easier than ever to adopt modern DNS security.

Microsoft 365 Messaging Team

High Volume Email is Generally Available and Ready to Charge

TonyRedmond — Thu, 23 Apr 2026 08:31:39 GMT

On April 1, Microsoft announced the general availability for the High-Volume Email (HVE) solution together with details of the PAYG charges incurred to send email to internal recipients, which is all that HVE can do. Microsoft will enable HVE charging on June 1, 2026, Before then, you’ll need to create a billing policy and link it to a valid Azure subscription if you want to continue to use HVE.

https://office365itpros.com/2026/04/23/hve-ga-charging/

Is the Archive mailbox self-help diagnostic working for anyone?

RyanSteele-CoV — Tue, 21 Apr 2026 21:07:40 GMT

Just curious: is the archive mailbox self-help diagnostic at https://aka.ms/PillarArchiveMailbox working for anyone?

When I run it, instead of getting results about the user whose UPN I entered, I get this:

The following issues were found with your archive mailbox.
No account was found for [The UPN of my admin account]. Make sure you've entered the correct email address or create a new account with that name. For more information, see Add users to Office 365.

I tried opening a ticket with Microsoft Support, but they refused to work on it without requiring me to do all the legwork of gathering logs and HAR traces and who knows what else, despite the fact that the support agent was able to replicate the exact same issue in his lab.

Change Optics Report released into Public Preview to showcase messages impacted by future changes

The_Exchange_Team — Mon, 20 Apr 2026 16:03:10 GMT

Change Management is an important part of managing the improvements we make to our service that may sometimes disrupt our customers. The key is empowering customers to identify if they have messages that will be affected when we announce changes to the service. To that end, we’d like to announce the Public Preview for the Change Optics Report. It will be the central location for finding messages that could be affected by future changes to the service.

As we improve or identify issues in Exchange Online, there is now a report to point customers to when we announce changes that could affect the sending and delivery of certain messages. This report will showcase multiple scenarios of interest and importance to admins preparing for change. It displays a sample set of messages that have the characteristics that match those expected to be affected.

These example messages give admins the information necessary to launch investigations that highlight where actions are needed to avoid disruption to their organizations as changes arrive. The report can then be used to observe the progress made to reduce those messages to a point where the risk has been removed ahead of the related change.

Initial Scenarios

The report is being released with two scenarios already included.

OMC represents Onmicrosoft.com traffic being sent externally. This is aimed at customers from large organizations still seeing usage they need to address before the traffic is throttled. For more information, see Limiting Onmicrosoft Domain Usage for Sending Emails | Microsoft Community Hub.
DRS represents Direct Send traffic being received by an organization’s tenant. This is useful for customers looking to use the Reject Direct Send setting and needing to first ensure all legitimate traffic is identified and catered for. For more information, see Introducing more control over Direct Send in Exchange Online | Microsoft Community Hub.

Using the report

The report can be found in the Exchange Admin Center (https://admin.cloud.microsoft/exchange) under Reports > Mail flow > Change Optics Report

Change Optics Report: Use this report to view changes made to your Exchange Online configuration over time. You can filter by date range and change type to find specific changes.

The report is divided into a Summary page and Details page.

Summary Page

This provides a summary chart tracking the volume of messages flag by the various scenarios being tracked.

Details Page

The Details page allows you to see example messages per scenario. The main message properties are available for use in an investigation, and the table can be exported. Message Trace can be used to retrieve any additional information needed about a message.

The scenario you are interested in can be selected from the dropdown menu.

Please provide any feedback in the Comments section. We will update this blog to announce when the report reaches GA.

Microsoft 365 Messaging Team

User cannot rename categories even when being the owner

mateusz_pawlik_skf_123 — Mon, 20 Apr 2026 10:03:16 GMT

Hi guys,

I have a user that cannot rename categories in a mailbox whilst being the owner.

As you can her permission level is set on owner.

And yet the rename is greyed out:

User says she was able to rename just some time ago, but when she tried on 17/04/2026 she couldn't. Anyone has any ideas?

Announcing Period 2 Exchange 2016/2019 Extended Security Update (ESU) program

The_Exchange_Team — Wed, 15 Apr 2026 14:35:11 GMT

While both Exchange 2016 and 2019 are out of support since October 2025, some of our customers who needed more time to finalize migrations to Exchange Subscription Edition (SE) have opted to enroll into the Extended Security Update program. That ESU program started in October 2025 and is ending in April 2026 (“Period 1”).

As end of April 2026 nears, some of our customers told us that they needed additional time to finalize their Exchange 2016/2019 migrations.

Today we are announcing that we created a “Period 2” Exchange Server ESU program. This period will last from the start of May 2026 through the end of October 2026 (6 months). There will be no further extensions of this program after that.

Conditions of Period 2 Exchange ESU program

Customers who wish to enroll into Period 2 program will have to re-purchase the Exchange ESU contract even if they were already enrolled into the Period 1 ESU program (October 2025 – April 2026). Period 2 is not an “extension” of current Period 1 Exchange ESU program (which ends in April 2026). Your organization does not automatically enroll into Period 2 – you will have to purchase the ESU again for additional 6-month coverage through October 2026 (in the same way that you purchased the original ESU).
In Period 2, we plan to provide security updates for Exchange Server 2016 CU23 and Exchange Server 2019 CU14/CU15.
Any Exchange Server ESUs purchased starting with today’s date (April 15, 2026) will automatically be considered Period 2 and will be valid from May to October 2026. Your organization will receive information on how to download updates released under Period 2 ESU (your original ESU program instructions will not work for ESU updates released after April 2026).

Starting today, customers can contact their Microsoft account team to get information about and purchase additional Period 2 Extended Security Update (ESU) for their Exchange 2016 CU23 or Exchange 2019 CU14/CU15 servers. Simply purchase the same product after today’s date. Your account teams will have information related to per server cost and additional details on how to purchase.

What does this mean?

This ESU is not an “extension of the support lifecycle” (Microsoft Lifecycle Policy | Microsoft Learn) for Exchange 2016 / 2019. Those servers are still out-of-support, and you will not be able to open support cases for them (unless directly related to an issue with an update released to ESU customers during the ESU period).
This Period 2 ESU is a way for customers who might not be able to finalize their Exchange 2016 or 2019 migrations to Exchange SE before the end of October 2026, to receive Critical and Important updates (as currently defined by Microsoft Security Response Center (MSRC) scoring) as security updates (SUs) that we might release during Period 2. If there are SUs that we need to release, we will privately provide such SUs to ESU customers only.
We are not committing to actually releasing any SUs during the Period 2 ESU. Exchange Server does not necessarily receive SU updates every month on Patch Tuesday (2^nd Tuesday of the month) as SUs are released only if there are Critical or Important security product changes. Therefore, if there are no SUs that we need to release during the time of ESU program, there will be no such updates provided. We will, however, confirm with ESU participants each Patch Tuesday whether an SU was provided or not.
This Period 2 Exchange ESU will be valid until end of October 2026.

Who is Period 2 Exchange ESU for?

This program is intended for customers with a Microsoft Enterprise Agreement (EA) who are unable to finalize their Exchange 2016 or 2019 migrations to Exchange SE before end of April 2026 and still need Critical and Important security coverage for servers still in operation.

FAQs

Why does Microsoft require additional contract for Period 2 of Exchange ESU if our organization already has the original Exchange Server ESU?
Period 2 is a separate contract that lasts until the end of October 2026. Many of our original ESU customers are finalizing their migrations by end of April 2026. Those few that need additional time have an option of getting a new ESU contract. Our preference is that our customers finalize their migrations instead (honestly – we’d be happy to not sell Period 2 Exchange ESU to anyone; please migrate instead!)

Our organization did not purchase original Period 1 Exchange ESU (ending with April 2026). Can we purchase Period 2 ESU only?
Period 2 ESU is separate from original Period 1 ESU and can be purchased independently. Purchasing the Period 2 ESU does not require purchase of Period 1. But note that purchase of Period 2 ESU will only get you update packages released after Period 2 starts. You will not get access to update packages released during Period 1 ESU. Seeing that all our updates are cumulative, fixes for issues released during Period 1 ESU will be included in Period 2 updates (when / if released).

How is Exchange Server ESU licensed and how are updates distributed?
Updates released under Period 2 Exchange ESU will follow the same process as updates released under the Period 1 ESU program: once enrolled, your organization will be provided information on how to access any updates released under Period 2. There will be no special licenses or keys in the Microsoft 365 admin center or Volume Licensing. After purchase of Period 2 SKUs, you will receive a new ESU User Guide which will contain everything you need.

Our Exchange server is getting throttled or blocked when sending email to Exchange Online. How can Microsoft not make ESU updates available to all customers, so they can address this?
If your server is currently affected by Throttling and blocking of persistently vulnerable Exchange servers that indicates that the version currently running in your organization is roughly a year out of date. To resolve the throttling or blocking immediately, please install October 2025 (last publicly available) updates for Exchange 2016 or 2019. ESU updates are not required. There will come a day when October 2025 updates too will be throttled or blocked, but that is not currently the case. But note that even if you update to October 2025 updates your server is still out of support and out of date and you should migrate to a supported version ASAP.

Our organization has Microsoft Volume Licensing. Do we get the Exchange ESU automatically? Where can we buy Exchange ESU?
Exchange ESU program is a separate contract that each organization must explicitly purchase via their Microsoft account team (requires Microsoft Enterprise Agreement). Exchange ESU is not automatically included in Volume Licensing or Software Assurance.

Help! We purchased the ESU (Period 1 or Period 2) – but we do not know how to access the updates we paid for!
If you have already purchased the ESU and need information on accessing the latest Security Updates, please contact us by sending an email to ExchangeandSfBServerESUInquiry@service.microsoft.com. You are welcome to add your account team to the email also.

Please continue migrating to Exchange SE instead of taking advantage of this Period 2 ESU program. But if you really must, contact your Microsoft account team for more details on Period 2 ESU.

A similar program extension is available for our Skype for Business 2015 / 2019 customers. Please read more here.

The Exchange Server Team

No Exchange Server Security Updates for April 2026

The_Exchange_Team — Tue, 14 Apr 2026 16:58:13 GMT

Although Exchange 2016 and 2019 are now out of support, some customers have purchased the Exchange 2016 and 2019 Extended Security Update (ESU). We have therefore decided that until the end of this Exchange 2016 and 2019 ESU period (April 2026) we will make an explicit update related announcement even if we DO NOT release anything for that particular month.

There are no security releases for any version of Exchange Server in April 2026, for customers with Exchange SE, or Exchange 2016 or 2019 ESU.

Please keep upgrading your organizations to Exchange SE.

The Exchange Team

Email Showing as Quarantined in a Message Trace, but Not Showing up in MS Defender

duntlessOutlook — Thu, 09 Apr 2026 19:23:13 GMT

A customer of ours was waiting on an email to arrive and to help figure out where the email was or if it was sent yet we ran a message trace. The message trace showed that the email was sent to quarantine. With this information in mind, I went to MS Defender > Email & collaboration > Review > Quarantine but could not find the message.

I modified some of the filters and could not get the quarantined message to appear. I triple checked the filters I created and made sure the information was correct. I also removed all filters and looked for the time period the email came in, but could not find it.

Not sure if this is related, but this email had a significant delay likely coming from the sender.

Any thoughts or ideas? Or anything that I am missing?

Administratively retract a user's email

TomCSB — Wed, 08 Apr 2026 12:12:12 GMT

I was recently asked to retract a message that was sent in-error to staff. I ran a discovery/search, and saved it, but when I ran the powershell script after connecting to Exchange, the script could not find the search, something like name not found. I verfied the name was correct, and I am a global admin so permissions should not have been an issue.

Does anyone know of any accurate documentation to run a search and retract? I had to use an old YouTube video and could not find anything in Microsoft's documentation.

ARC verification fail (40) on specific Exchange Online frontends - recurring issue

darkglobe — Mon, 06 Apr 2026 10:56:42 GMT

Hello,
We are observing recurring arc=fail (40) errors on messages forwarded through Exchange Online, caused by specific frontend servers. The same messages pass ARC verification correctly on other providers (Google, etc.).

Affected frontends identified so far:

CH2PEPF0000013F.namprd02.prod.outlook.com - build 15.20.9700.17 (March 14, 2026)
CH3PEPF0000000B.namprd04.prod.outlook.com - build 15.20.9769.17 (April 6, 2026)

Both share the same build suffix .17. The signing implementation on our side has been cryptographically verified as correct and RFC 6376 compliant. The issue has also been reported on the IETF ietf-smtp mailing list with full technical analysis.
Cryptographic analysis shows the failing servers append a spurious trailing \r\n to the last header before computing the verification hash, violating RFC 6376 Section 3.7.

Is there a pattern with .17 frontend builds and ARC verification?

Reagards
Vittorio

Microsoft Exchange Report

atanudutta007 — Sun, 05 Apr 2026 12:27:58 GMT

I faced a new issue today, don't know if anything breaks at Microsoft or any new thing roll out from there, the things is unable to check usage report properly as well as unable to export the email activity, Mailbox Usage etc report under report- exchange and other tabs as well in customer tenant.

I have Global Reader privilege but still facing this issue. Anyone faced this type of issue from today or before? If anyone knows about its pleas update your comment here.

Thanks..

iOS 26.4 iPhone Contact Sync with Microsoft Exchange Online

fbatuns — Wed, 01 Apr 2026 12:59:26 GMT

For the past 2–3 weeks, several of our iOS users have been experiencing synchronization issues with Exchange contacts. Contacts intermittently disappear from their devices and then re-sync after some time. In some cases, the re-synchronization process is significantly delayed. Anyone else experiencing the same issue?

Preserving permissions during EXO migration

Naxiu — Wed, 01 Apr 2026 06:46:40 GMT

Hi,

Can you help me understand the outcome of preserving the permissions in our scenario.

Exchange Server 2016 (soon Exchange SE) in a hybrid with Exchange Online.
We are moving 75% of the mailboxes to Exchange Online.

What ways will preserve or break the full-access or sendas permissions?

I guess best way would be to migrate both the user and the shared mailbox at the same time in the same batch to keep the permission?

If we migrate the user in batch 1 and shared mailbox in batch 2 will that preserve/break the full access/send as?

If we migrate the shared mailbox in batch 1 and usermailbox in batch 2 will that preserve/break the full access/send as?

If the permission is linked directly on the shared mailbox or via a security group is there a difference?

Thanks!

High Volume Email reaches General Availability in Exchange Online

Nino_Bilic — Wed, 01 Apr 2026 13:25:49 GMT

As we discussed High Volume Email (HVE) several times since it was in Public Preview, I wanted to make you aware that Exchange Online HVE now reached General Availability (GA) in our multi-tenant (WW) service. The announcement was made on the Microsoft 365 Blog here:

High Volume Email Is Now Available in Exchange Online

Pricing is discussed in the announcement above.
HVE documentation can be found here.

Nino Bilic

Microsoft Limits App Access to Sensitive Message Properties

TonyRedmond — Thu, 26 Mar 2026 13:43:43 GMT

Microsoft has announced details of a change to app permissions to restrict updates to sensitive message properties (like recipients) without consent for a new advanced mail access permission. If tenants have apps that interact with message properties, including apps developed by third parties, they should check whether the apps are updating sensitive properties. If so, the new permission must be assigned or the apps will stop working.

https://office365itpros.com/2026/03/26/sensitive-message-properties-graph/

Can we hide default address lists in Outlook Address Book and show only custom ones?

Como_L — Wed, 25 Mar 2026 07:05:00 GMT

There are existing Custom Address Lists. When users use the MS Outlook App (Office 2019) and open the Address Book, is it possible to hide the other address lists (including domain-sg-GAL, Global Address List, and domain-sg-Rooms), and only display the Custom Address Lists (domain-HK-AL and domain-sg-AL) — the ones shown in green in the photo?

Upcoming Breaking Changes to Modifying Sensitive Email Properties via Graph API

The_Exchange_Team — Tue, 24 Mar 2026 16:05:53 GMT

We are implementing a significant update in our service affecting applications that modify sensitive properties on non-draft email messages. These sensitive properties include the subject, body, recipients, and a number of other properties when changed using any of the message update methods on Graph API.

Immutability of Received Email Messages

There is a fundamental expectation that once an email message has been received, it should remain unchanged except for specific management-related properties such as read status, flags, and similar attributes. Critical components like the address list, subject, and body text should not be altered unless a new draft message is created. Exceptions to this rule are specialized use-cases, particularly within the security domain, such as identifying suspicious emails and other privileged operations.

Required Permissions for Modifying Sensitive Properties

To maintain the expected immutability of email messages during standard management operations, we will begin restricting applications from modifying sensitive message properties in non-draft messages unless they possess elevated permissions. Specifically, applications must have one of the following permissions: Mail-Advanced.ReadWrite, Mail-Advanced.ReadWrite.All, or Mail-Advanced.ReadWrite.Shared, depending on the scenario. All these permissions require a tenant administrator consent.

The documentation page identifies sensitive properties as those that are only updateable if isDraft = true. Once the restriction goes into effect, these properties can only be updated in non-draft messages if the application has Mail-Advanced.ReadWrite permissions. Draft messages will continue to be updateable with the current Mail.ReadWrite permissions.

Timeline and Recommendations

These required permissions are already available. Enforcement of the new restrictions in our service – blocking Graph API updates to sensitive email properties – will begin on 12/31/2026. If you develop Graph API applications that modify these properties, we strongly recommend updating your applications to request the necessary higher-level permissions as soon as possible. This proactive approach will help ensure a smooth transition and minimize potential disruptions for your customers.

The Exchange Team

Celebrating 30 Years of Microsoft Exchange

The_Exchange_Team — Mon, 23 Mar 2026 17:00:06 GMT

It’s hard to believe, but Exchange Server is now 30 years old! A lot has changed since the first release of Exchange Server 4.0 in 1996: protocols, platforms, scale, and even what “email” means in the modern workplace.

To commemorate this milestone anniversary, we want to pause and reflect on how Exchange has shaped enterprise email as we know it today.

The start: email becomes enterprise messaging

Back in the mid-1990s, messaging solutions were fragmented, proprietary, and difficult to manage at scale. Businesses looking for a messaging system basically had two choices: host-based systems that were costly and didn’t integrate well with PC-based applications or LAN-based systems that did integrate with PC-based applications but were less scalable and reliable (although there were several companies that made software that allowed different email systems to communicate).

That changed when, after nearly four years of development, Microsoft Exchange Server 4.0 – “the e-mail server with integrated groupware that makes it easy to communicate” – was released on April 2, 1996. Or, it might have been March 1996. Or maybe June 1996. No one knows for sure because the first public build that was shipped was not the build on the gold master (the signed-off RTM version).

Nonetheless, Exchange Server had ambitions! From the start, it combined email and calendaring as well as an integrated centralized directory. Admin controls and native support of Internet standards like SMTP (via Internet Mail Connector) and X.400 kept it “modern.”

In addition to user productivity through email, Exchange provided admin controls for monitoring, managing, and troubleshooting messaging across an entire organization from a single system – an idea that now seems obvious, but was far from standard in 1996.

Exchange shapes the market

As Exchange evolved through the late 1990s and early 2000s, it kept raising the bar for business email. It was during this time that several major changes occurred:

Email and user identity became inseparable. This directly influenced the development of Active Directory (Active Directory was the direct descendant of the Exchange Directory Service).
Calendaring and scheduling were first-class workflows and not bolt-on experiences.
Reliability, scale, and disaster recovery became built-in
Administrators came to expect the ability to automate admin tasks.

Exchange Server became one of Microsoft’s first truly successful enterprise server products, helping establish us as a serious enterprise platform provider beyond the desktop.

The foundation of Exchange Online

When we set out to build Exchange Online (remember Exchange Labs?), the goal was to operate enterprise email as a global service.

Exchange Online inherited many years of lessons from Exchange Server as it extended to the service. That continuity of experience is one reason our customers were able to move from Exchange Server to Exchange Online more confidently as they worked with already familiar tools. Concepts such as mailboxes, the transport pipeline, policy enforcement, and compliance remained familiar, even as the operational model changed. Exchange quite literally became the backbone of Microsoft 365’s compute, routing, and storage (also known as the Substrate).

Exchange Server still matters in 2026

Three decades later, Exchange Server still matters. Conversations around digital sovereignty, regulatory compliance, and admin control continue. Many organizations like governments, regulated industries, and critical infrastructure providers must make choices about where their data is stored and who operates the infrastructure.

For customers that need it, Exchange Server remains valuable as an architectural choice. Continued investment in Exchange Server, including release of Exchange Subscription Edition (SE) which we are committed to supporting until at least the end of 2035 reflect the reality that enterprise messaging is not one-size-fits-all.

Cloud-first (where innovation is the fastest) does not need to mean cloud-only. Whether you want to run on-prem, hybrid, or cloud, Exchange is there for you.

Through it all, community helped shape Exchange

While this is a bit intangible, we want to acknowledge that feedback from Exchange admins, MVPs, partners, and customers influenced (and keep influencing) Exchange in real ways. Feedback via our blog (since the first post, back in 2004), support cases, and feedback given through conferences or Feedback portal over the years really matter. Some design changes happened specifically because the community spoke clearly. Our teams staying involved (via, for example, this blog) has been extremely valuable to us. Please keep giving us feedback!

How things are changing

Exchange backward compatibility was both a gift and a burden. For many years, we allowed customers to have coexistence of 3 major Exchange versions within the same organization. This helped reduce migration pain. But it also slowed down architectural cleanup and modernization as every version had to play nice with choices made years earlier. We are looking forward to the future in which we support only a single major version inside an organization – Exchange Subscription Edition (SE) – a requirement we are adding starting with Exchange SE CU2!

Security came into focus over the years. It is still in focus. Early Exchange was built for connectivity and collaboration. The threat model changed, with threat actors going after organizational email. It is more important than ever to stay up to date. We realize that some upcoming security changes mean that admins need to do additional work (for example upcoming hybrid security improvements), but the result will be your organization’s improved security posture.

With all the modes of communication that have become popular in business environments over the last 3 decades, the “end of email” has been predicted many times. Yet, email is still alive. And judging by our inboxes, it’s thriving!

We want to thank the admins, MVPs, partners, and customers who keep Exchange running and who’ve provided unfiltered feedback along the way. We are excited to continue this journey with you!

Here are a few fun Exchange historical posts that you might have missed over the years:

And a few technology-specific fun posts related to Exchange history:

From crush to product documentation: The story of Squeaky Lobster
Me Too!
Why is OOF an OOF and not an OOO?
The saga of the M: drive
The BillG bit in AD
The Autodiscover Song
How the Exchange 2007 icon was made
The excitement of dogfooding Exchange at home
The secret decoder ring
The other secret decoder ring
The 2.4 GB message successfully delivered by Exchange Server 2003
The Exchange Team answering the citation call from Wikipedia
Ask Perry/Geek Out with Perry
Investigating replacing ESE with SQL

The Exchange Team