Engadin Airport

Title: Users may be unable to access archived email messages in Outlook on the web

User impact: Users may be unable to access archived email messages in Outlook on the web.

Final status: We've validated the fix has completed deployment to all affected environments. However, users that reported the issue haven't responded to validate that our corrective actions resolved the issue. In the event impact persists, please contact one of our support representatives so we can continue our investigation into the problem.

Scope of impact: Impact is specific to some users attempting to access archived email messages in Outlook on the web.

Start time: Tuesday, March 24, 2026, at 9:37 AM UTC

Root cause: A code issue is resulting in restricted access when archiving email messages in Outlook on the web. The primary and archive mailboxes are on different machines, the request to access the mailbox is landing in the correct portion of infrastructure but is trying to find the primary instead of the archive mailbox, resulting in impact.

This is the final update for the event.

Title: Some users may see unwanted add-ins appearing automatically across all Outlook clients

User impact: Users may see unwanted add-ins appearing automatically across all Outlook clients.

More info: These add-ins are configured to be available to users by admins but aren’t expected to be automatically installed. To bypass this issue, admins can run the “Set-App -Identity -OrganizationApp -PrivateCatalog -DefaultStateForUser Disabled” command to remove add-ins that are unintentionally appearing.

Current status: Our deployment is taking longer than initially expected and we now anticipate deployment to be fully completed by Monday, October 5, 2026. We anticipate the majority of users to be remediated at this time while we complete our deployment.

Scope of impact: Impact may occur for some users that are viewing their add-ins across all Outlook clients. This section may be updated as the investigation progresses.

Start time: Friday, July 17, 2026, at 10:26 AM UTC

Estimated time to resolve: We anticipate impact to be resolved by Monday, October 5, 2026.

Root cause: A portion of the Exchange Online add-in sync pipeline isn't processing add-in state information as expected. This is causing incorrect EnabledStatus values being returned and Outlook automatically displaying add-ins configured as Available, which is resulting in impact.

Next update by: Monday, October 5, 2026, at 7:00 PM UTC

Title: Some users may be unable to search for email in Outlook desktop and Outlook on the web

User impact: Users may be unable to search for email in Outlook desktop and Outlook on the web.

Current status: Our deployment of configuration changes to remediate impact is continuing and taking slightly longer to fully saturate than anticipated. We'll continue to monitor its deployment and provide an updated remediation timeline as soon as one becomes available.

Scope of impact: Some users attempting to search for Exchange Online email in the Outlook desktop client and Outlook on the web may be impacted. This information may be updated as our investigation continues.

Root cause: The portion of service infrastructure responsible for facilitating the Outlook search is receiving increased request traffic, which is preventing the service from being able to handle the traffic in an efficient manner and is causing impact.

Next update by: Thursday, October 1, 2026, at 8:00 PM UTC

Title: Admins experience intermittent failures adding, modifying or removing members from Exchange Online distribution groups

User impact: Admins experience intermittent failures adding, modifying or removing members from Exchange Online distribution groups.

More info: Admins may intermittently receive an error stating, "Failed to update Members - Response Content is Null" when managing distribution group membership in the Microsoft 365 Admin Portal or Exchange Admin Center.

As a workaround, admins can use Exchange Online PowerShell to add or remove members from affected distribution groups.

Impact is specific to admins utilizing on-premises Exchange who are attempting to add or remove members from Exchange Online distribution groups.

Current status: We're deploying a code fix to our internal test environment to validate its efficacy in remediating the impact. We anticipate our validations will be completed by our next scheduled communications update, at which time we'll aim to provide a timeline for the broad deployment.

Scope of impact: This issue impacts some on-premises Exchange admins attempting to add or remove members from Exchange Online distribution groups. This section may be updated as the investigation progresses.

Start time: Tuesday, June 9, 2026, at 9:43 PM UTC

Root cause: A conflict between a configuration and a recent update is preventing admins from adding or removing users from distribution groups for on-premises configurations.

Next update by: Thursday, October 1, 2026, at 5:30 PM UTC

Title: Users may be unable to update calendar delegates in the classic Outlook desktop client

User impact: Users may be unable to update calendar delegates in the classic Outlook desktop client.

More info: As a workaround, affected users can manage delegate changes through Outlook on the web.

Current status: Our deployment is at 62 percent saturation, and we anticipate deployment to be complete by our next scheduled update.

Scope of impact: Impact is specific to users that are unable to update calendar delegates in the classic Outlook desktop client. This information may be updated as our investigation continues.

Start time: Wednesday, September 23, 2026, at 7:13 AM UTC

Estimated time to resolve: We anticipate impact to be resolved by our next scheduled update on Thursday, October 1, 2026, at 10:00 PM

Root cause: A recent update to the service contained a regression, resulting in this impact.

Next update by: Thursday, October 1, 2026, at 10:00 PM UTC

Title: Some users’ email messages may not be quarantined and fail to be stored in the quarantine folder

User impact: Users’ email messages may not be quarantined and might fail to be stored in the quarantine folder.

More info: The following error appears in message trace: '‎550 5.1.10 Failed to deliver to Quarantine store‎'.

Current status: We've identified a recent service-side update that introduced an impacting code error that's causing some email messages to not be quarantined and fail to be stored in the quarantine folder. As we develop a code fix to remediate the impact, we're exploring a secondary potential mitigation option involving moving affected service traffic. We're expecting more clarity into our mitigation action plan by our next scheduled communication update.

Scope of impact: This issue may impact users attempting to have email messages quarantined in Exchange Online. This section may be updated as the investigation progresses.

Root cause: A recent service-side updated unintentionally introduced a code error that has caused this impacting event.

Next update by: Thursday, October 1, 2026, at 1:00 AM UTC

Title: Users may be unable to reply or reply-all to email messages sent to Microsoft 365 groups in Exchange Online

User impact: Users may be unable to reply or reply-all to email messages sent to Microsoft 365 groups in Exchange Online.

More info: As a temporary alternative, impacted users may reply or reply all to email messages through user inboxes.

Current status: We've initialized our fix deployment to the affected environment and anticipate the impact should be fully remediated by our next scheduled update.

Scope of impact: This issue impacts any user attempting to reply or reply-all to email messages sent to Microsoft 365 groups in Exchange Online. This information may be updated as our investigation continues.

Next update by: Tuesday, October 6, 2026, at 1:00 AM UTC