Exchange topics

Microsoft Finally Makes Send Mail from Alias Generally Available

TonyRedmond — Fri, 09 Oct 2026 08:12:16 GMT

Nearly five years after going into preview, Microsoft has made the send from alias feature for Exchange Online generally available. It’s a very useful feature that eliminates the need to use a shared mailbox to be able to send messages with different email addresses. Microsoft has closed some functionality gaps since the preview started, but sending from an alias is not the same as sending from a mailbox’s primary SMTP address. Some user training might be necessary!

https://office365itpros.com/2026/10/09/send-from-alias-finally-ga/

Why do Apple macOS and Ubuntu clients display Exchange meeting times one hour earlier than scheduled

Yasir_khan — Fri, 09 Oct 2026 05:59:29 GMT

If a meeting is generated from Apple macOS and Ubuntu clients showing the meeting time as one hour earlier than the actual scheduled time email solution is exchange server 2019, what will be the issue.

Staff Email hacked Restored but not able to receive any emails

Seena_Poopathi — Thu, 08 Oct 2026 20:32:07 GMT

Could you please advise on the best way to restore emails for a staff member whose email account was recently compromised? I am the account administrator and am trying to recover any missing messages and verify mail flow. I have already used Message Trace, but I can't locate a test message I sent to the user. Any guidance on the appropriate recovery steps or troubleshooting recommendations would be greatly appreciated. Thanks

Unable to Locate email in Quarantine List

robcol — Thu, 01 Oct 2026 13:48:53 GMT

Message Trace shows the email is in Quarantine. When I go to the admin Quarantine List, I am unable to locate email in Admin Quarantine List.

Using PowerShell to Work with Microsoft 365 Groups, Conversations, Threads, and Posts

TonyRedmond — Wed, 30 Sep 2026 10:59:12 GMT

When launched in 2015, Outlook groups were an email-based collaboration platform. Now called Microsoft 365 Groups, the few Outlook groups that host email-based discussions have a distinctive Graph API to create and manage the conversations, topics, and posts which make up their discussions. This article reviews how to use PowerShell to fetch these objects and how to create new conversations and reply to posts (using the Outlook Groups APIs, of course).

https://office365itpros.com/2026/09/30/outlook-group-graph-api/

Microsoft to Drop Most Azure Communication Services

TonyRedmond — Tue, 29 Sep 2026 13:39:40 GMT

Microsoft has announced that it will retire most Azure Communication Services offerings on September 30, 2028. Among the affected services is Email Communication Services (ECS), leaving Microsoft without a dedicated cloud service for high-volume external email. Exchange Online’s High Volume Email (HVE) service currently lacks that capability, but Microsoft could choose to fill the gap with a new pay-as-you-go HVE offering aimed at bulk email workloads.

https://office365itpros.com/2026/09/29/acs-retirement-sept-2028/

Cross-Tenant Mailbox Migration - HTTP 401 Unauthenticated during Test-MigrationServerAvailability

Malextrimo — Mon, 28 Sep 2026 10:17:24 GMT

We are performing a Cross-Tenant Exchange Online mailbox migration between two Microsoft 365 tenants.

The migration endpoint is configured with ApplicationId authentication and validates successfully.

When running:

Test-MigrationServerAvailability -Endpoint "MexicoToPortugal" -TestMailbox "<user>"

the test consistently fails with:

StatusCode="Unauthenticated"

HTTP Status Code: 401

We reproduced the issue with two different users.

We have already validated:

- MailUser configuration

- ExchangeGuid

- LegacyExchangeDN (X500)

- ExternalEmailAddress

- Accepted Domains

- Organization Relationships

- Migration Endpoint

- Enterprise Application

- Mailbox.Migration permission

- Admin Consent

- Cross-Tenant Migration licensing

The same HTTP 401 error occurs for multiple mailboxes after all configuration issues are corrected.

Has anyone experienced a similar Cross-Tenant Mailbox Migration scenario where Test-MigrationServerAvailability returns HTTP 401 Unauthenticated even though the Enterprise Application, Mailbox.Migration permission and Admin Consent are correctly configured?

Retirement of Azure Communication Services

Zohaib_Yousuf — Sun, 27 Sep 2026 06:02:05 GMT

Microsoft has announced several retirement and breaking changes in September 2026.
One notable change is the retirement of Azure Communication Services as a standalone offering, scheduled to take effect on September 30, 2028.

Organizations currently using Azure Communication Services should review the announcement, assess the potential impact on their environments, and begin planning accordingly.

https://learn.microsoft.com/en-us/azure/communication-services/acs-retirement-and-breaking-changes-guide

Exchange 2019 Recovery Monitoring Mailboxes

Amina28 — Wed, 23 Sep 2026 12:08:22 GMT

Hello, everyone!

I have a geographically distributed DAG cluster consisting of two Exchange 2019 CU15 servers.

Problem:

Monitoring Mailboxes are not being created on either server.

What I’ve already checked:

I stopped the following services:

Microsoft Exchange Health Manager

Microsoft Exchange Health Manager Recovery

Business Standard with Exchange Plan 2 NOW only showing 100GB of email space

JimOh — Sun, 20 Sep 2026 23:23:22 GMT

FOR THE PAST 3 YEARS, we have 15 users with Microsoft Business Standard with 100GB of email storage space and 11 with Microsoft Business Premium with 100GB of email storage. I have 1 Business Standard with Exchange On-line Plan2, and 1 with Exchange On-line Plan2. Both have always jhad 150GB of usable mailbox storage. Both users for several years, leading up to September 18, 2026 had over 100GB of mail in their mailboxes and had no problems sending or receiving email, ever. THEN ALL OF THE SUDDEN on 9/18/2026, these 2 users with Plan 2 are no longer able to receive any email and it now shows their mailbox is full Even though checking active users details about mail for both of these users shows 150GB storage. In investigating further, in the exchange area of the admin portal, checking mailboxes indeed both of these 2 USERS ONLY SHOW 100GB, which is the exact same as all my other users who are not paying for Exchange PLAN 2. HOW DO I REPORT this to Microsoft?

IMAP Mail Migration

Gagandeepkaur370 — Tue, 15 Sep 2026 05:12:15 GMT

Hello Microsoft Community,

We are currently performing a mailbox migration from Google Workspace (Gmail) to Microsoft 365 Exchange Online using the IMAP migration method.

The customer's environment is configured for split routing/coexistence, where both Google Workspace and Microsoft 365 are actively being used during the migration process. Mail flow is functioning as expected; however, we are experiencing extremely slow migration performance.

For example, a mailbox containing approximately 10 GB of data is taking nearly two weeks to migrate, which is significantly impacting the overall project timeline.

We would appreciate guidance on the following:

Is this migration speed expected when using the IMAP migration method from Google Workspace to Exchange Online?
Does Exchange Online enforce any throttling limits that can affect IMAP migration throughput?
Can split routing or coexistence between Google Workspace and Microsoft 365 impact IMAP migration performance?
Is there a recommended number of concurrent mailbox migrations or migration batch size for optimal performance?
Are there any Google Workspace-side limitations, API restrictions, or throttling settings that should be reviewed?
What Microsoft-recommended configurations or best practices can help improve IMAP migration speed?
If higher migration throughput is required, does Microsoft recommend an alternative migration approach instead of IMAP?
If split routing/coexistence must remain active throughout the migration project, what is the recommended Microsoft-supported migration method?

We are trying to identify whether the bottleneck is on the Exchange Online side, Google Workspace side, or related to the coexistence configuration.

Any troubleshooting guidance, performance recommendations, or Microsoft documentation references would be greatly appreciated.

IMAP Migration from Google Workspace to Microsoft 365

akanksha2 — Mon, 14 Sep 2026 07:22:45 GMT

Hello Team,

Greetings!!

We have recently been experiencing significant delays during IMAP migrations from Google Workspace to Microsoft 365 and would like to understand if there are any known issues or recent changes affecting IMAP migration performance.

We are aware that Microsoft provides the native Google Workspace migration method, which would generally be preferable. However, in our migration scenarios, we have split routing/coexistence configured, with the domain configured as Internal Relay in Exchange Online. Because of this setup, we are currently unable to select/configure the required target delivery domain as expected during the native Google Workspace migration process.

Could you please confirm:

Whether there are any known issues, throttling, or performance degradation with IMAP migrations from Google Workspace to Microsoft 365 recently?

Whether the Internal Relay/split-routing configuration can affect the native Google Workspace migration process or the availability of the target delivery domain option?

Is there any recommended configuration or workaround that would allow us to use the native Google Workspace migration while maintaining split routing?

Any guidance or recommended approach would be highly appreciated.

Sincronizzare scheda contatti dell'account di posta elettronica con active directory

ALCANTAREX — Fri, 11 Sep 2026 05:10:05 GMT

Good morning,

I need to update the mobile and office phone numbers for users in Active Directory and then synchronize them with the contact information in their email accounts. The goal is to ensure that when a user types an email address in Outlook and hovers their mouse over it, the phone and mobile numbers are visible in the contact card.

Microsoft Bumps Auto-Expanding Archive Limit Past 1.5 TB

TonyRedmond — Thu, 10 Sep 2026 08:46:23 GMT

First revealed in 2015, the history of auto-expanding archives in Exchange Online has been spotty with several false starts. Now the limit will go past 1.5 TB, but only for eligible E5 licenses. Although the roadmap item has roll-out scheduled for October 2026, Microsoft hasn’t revealed details of what the new upper limit will be or how the new limit will be managed. Having a massive archive mailbox will never concern me, but there must be some who need such a monster archive.

https://office365itpros.com/2026/09/10/auto-expanding-archive-larger/

Exchange SE Published Calendar URLs giving HTTP 500 error (both html and ics)

jrsmith83 — Wed, 09 Sep 2026 18:00:24 GMT

I'm getting an http 500 error when trying to browse any published calendar url. I already recreated the owa virtual directories and just updated to the latest patch level of Exchange Server SE. I did a failed request tracing for error 500 and I see the following info:

When I got to that section of the web.config I see the following under rewrite:

I tried using AI to "fix" this but it didn't fix anything. Can anyone offer any insite as to what's wrong here?

Thanks!

p.s. this was getting listed as spam so I will paste the text from the pictures in a reply below

Own domain flagged as harmful by Safe Links — submissions return "Unknown"

Mijiddorj — Wed, 09 Sep 2026 02:37:50 GMT

Our organization's own domain is being flagged as "This message contains a link that might be harmful" in Outlook and Teams. We submitted the URL for review via Submissions → URLs twice (over several days apart), and both came back as "Unknown - We checked but can't make a decision right now." We also tried adding the domain to the Tenant Allow/Block List, but the warning in Teams still persists. Per the portal notice, tenant allow entries only override bulk/spam/regular phishing verdicts, not malware/high-confidence phishing — so we suspect the domain may be misclassified at a higher severity level. Has anyone experienced this before, or know how to escalate when submissions repeatedly return "Unknown"?

Submission IDs for reference: 5483d45c-405e-46c8-97e3-08df0cc793fb (Sep 7) and dcaab607-4ead-4791-4996-08df0a6ab25a (Sep 4).

Exchange online - shared personal calendar dissapear

AppleKri — Tue, 08 Sep 2026 05:01:19 GMT

User A has been given full delegate access to User B mailbox - set in exchange admin backend

When user A open OWA (or outlook app) - the calendar of User B does not show up.
Manually when adding User B calendar the calendar shows up - but only with limited view (details of meeting not shown)

If User A do a F5/refresh in OWA (or close and open outloo app) - the calendar of User B is gone again

Have tried to reset the rights on calendar of user B - so to remove all access for user A. And wait 24 hours - and then set the rights again.
But issue on calendar keep going on

Running exchange online

Outlook Classic Stamps Its Style on the New Outlook

TonyRedmond — Mon, 07 Sep 2026 08:12:46 GMT

In an attempt to ease the transition to the new Outlook, Microsoft has introduced the classic Outlook style for the new Outlook and OWA. The style essentially redoes the existing GUI for the web clients to make their appearance very close to the win32 client. After using the two clients side by side for a week, sometimes I find it difficult to know what client I’m interacting with. The question is what average users rather than IT people think of a different face for the new Outlook.

https://office365itpros.com/2026/09/07/classic-outlook-style/

Depreciation of Custom Controls in favor of External MFA

Zohaib_Yousuf — Sat, 05 Sep 2026 08:05:32 GMT

Deprecation of Custom controls
Custom controls are being deprecated in favor of External MFA. Existing configurations keep working during the transition, but you should begin migration planning now. Custom controls retire September 30, 2026, and reach end of life in May 2027.

When will you see this change?
Custom controls will be retired on September 30, 2026, and the service will reach end of life in May 2027.

Who will be affected by this change?
This update affects organizations currently using Custom controls to integrate third-party MFA providers with Conditional Access.

How will this affect your organization?
Organizations relying on Custom controls will need to transition to External MFA to maintain support and continue using third-party MFA solutions within Microsoft Entra ID. Moving to External MFA also enables more consistent Conditional Access enforcement and improved integration with Microsoft Entra security capabilities.

What do you need to do to prepare?
Organizations should:
Review existing Custom controls integrations
Evaluate External MFA migration requirements
Test Conditional Access policies and user experiences before migration
Begin migration planning ahead of the retirement date
Read more in the External MFA General Availability announcement and migration guidance.

Exchange Server OWA does not display lnline Images after EEMS M2.1.0 mitigation.

AnnTaeYoun — Fri, 04 Sep 2026 08:45:52 GMT

Exchange Server can automatically apply applicable mitigations by using the Exchange Emergency Mitigation Service (EEMS) to retrieve mitigation information from Microsoft's Office Config Service (OCS).

EEMS can apply several types of mitigations:

1. IIS URL Rewrite Rule Mitigation: Blocks specific malicious HTTP request patterns that could put an Exchange Server at risk.

2. Exchange Service Mitigation: Disables a vulnerable Exchange service.

3. Application Pool Mitigation: Disables a vulnerable application pool on the Exchange Server.

In this case, inline images were displayed correctly in Outlook, but the same images were not displayed in OWA.

The issue was identified as being related to the IIS URL Rewrite rule deployed by the M2.1.0 mitigation for CVE-2026-42897.

Verification

Run the following commands in the Exchange Management Shell.

1. Check the installed Exchange Security Update version

(Get-Command ExSetup.exe).FileVersionInfo.ProductVersion

2. Check whether the Emergency Mitigation Service is enabled

Get-OrganizationConfig | fl MitigationsEnabled

3. Check applied and blocked mitigations

Get-ExchangeServer | fl Name,MitigationsApplied,MitigationsBlocked

For example, a server affected by this issue may show:

MitigationsApplied : {PING1, M2.1.0} MitigationsBlocked : {M2.1.0}

4. Check the IIS URL Rewrite rule

Import-Module WebAdministration Get-WebConfigurationProperty -PSPath "IIS:\Sites\Default Web Site\owa" -Filter "system.webServer/rewrite/outboundRules/rule" -Name "." | Select-Object name

The following rule may be present:

EEMS M2.1 OWA CSP - outbound

Microsoft provides Security Updates (SUs) to address security vulnerabilities in Exchange Server. Exchange Server SE is currently supported, while Exchange Server 2016 and Exchange Server 2019 can continue to receive applicable security updates through the Extended Security Updates (ESU) program.

Note: Exchange Server 2016 and Exchange Server 2019 reached end of support in October 2025. ESU must be purchased separately to continue receiving applicable security updates.

Resolution

1. Install the July 2026 SU or later

Install the July 2026 SU or a later Security Update (preferably the latest available SU), and then restart the server.

Installing the update does not automatically remove the previously applied CVE-2026-42897 mitigation.

2. Block M2.1.0 from being reapplied

If M2.1.0 is not already listed under MitigationsBlocked, add it:

Set-ExchangeServer -Identity EXSE-01 -MitigationsBlocked @{Add="M2.1.0"}

Note: Adding M2.1.0 to MitigationsBlocked does not remove the IIS rules that have already been applied. It prevents EEMS from reapplying the M2.1.0 mitigation.

3. Back up the OWA web.config file

Copy-Item ` -Path "$env:ExchangeInstallPath\FrontEnd\HttpProxy\owa\web.config" ` -Destination "$env:ExchangeInstallPath\FrontEnd\HttpProxy\owa\web.config.$((Get-Date).ToString('yyyyMMdd-HHmmss')).bak"

4. Remove the M2.1.0 IIS URL Rewrite rule and precondition

Remove-WebConfigurationProperty ` -PSPath "IIS:\Sites\Default Web Site\owa" ` -Filter "system.webServer/rewrite/outboundRules" ` -Name "." ` -AtElement @{name="EEMS M2.1 OWA CSP - outbound"}

Then remove the associated precondition:

Remove-WebConfigurationProperty ` -PSPath "IIS:\Sites\Default Web Site\owa" ` -Filter "system.webServer/rewrite/outboundRules/preConditions" ` -Name "." ` -AtElement @{name="EEMS M2.1 OWA SPA HTML shell - precondition"}

Verification After Rollback

Without restarting the Exchange Server or running IISReset, reopen the same OWA message that previously failed to display the inline image and verify that the image is now displayed correctly.

Test Results

I reproduced the issue in an Exchange Server SE June 2026 SU test environment.

After EEMS automatically applied the M2.1.0 mitigation, an inline PNG image that was displayed correctly in Outlook was no longer displayed in OWA.

After blocking M2.1.0 and removing the M2.1.0 IIS rules according to Microsoft's rollback guidance, the inline image in the same message was displayed correctly again in OWA.

No Exchange Server restart or IISReset was required after removing the IIS rules.