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Title: Some users may be unable to access shared mailboxes from Outlook on the web

User impact: Users may be unable to access shared mailboxes from Outlook on the web.

More info: Users can access their shared mailboxes from the Outlook desktop client and Outlook mobile to avoid this issue. Additionally, if users are actively reproducing the issue on Outlook on the web, as a potential workaround we recommend users sign out of the session to ensure the existing cookies are cleared, then access Outlook on the web using the direct link for the shared mailbox, and sign in again.

Current status: We identified that an issue with a recent Outlook on the web build within our service infrastructure is causing some requests to access shared mailboxes to fail. We're developing a fix that will allow the requests to process as expected and remediate impact. Once the fix is ready, we'll validate it before deploying it to the affected infrastructure.

Scope of impact: Some users attempting to access shared mailboxes from Outlook on the web may be impacted.

Start time: Saturday, April 13, 2024, at 5:00 AM UTC

Root cause: A recent Outlook on the web build within our service infrastructure is causing some requests to access shared mailboxes to fail unexpectedly.

Next update by: Tuesday, April 16, 2024, at 11:00 PM UTC

Title: Users may be intermittently unable to download attachments or view embedded images in Outlook on the web

User impact: Users may be intermittently unable to download attachments or view embedded images in Outlook on the web.

More info: To ensure our mitigation takes effect, users will need to logout and log back into their Outlook on the web accounts. This issue may impact those who are downloading attachments or viewing embedded images in Outlook on the web.

Users may see the following error message when an attachment fails to download: “Error downloading the file content.” Downloading attachments and embedded image viewing may succeed after signing out and then back into Outlook on the web. If available, users can download attachments and view embedded images consistently through the Outlook desktop client or the Outlook mobile app.

Current status: We have verified the scope of impact for this event and our communications have been updated to ensure all of our affected tenants are informed of this issue. In parallel, our deployment of the fix is still ongoing and we expect that users will see relief as it reaches their environment.

Scope of impact: Users attempting to download attachments and viewing embedded images in Outlook on the web or Outlook mobile apps may be intermittently impacted.

Start time: Friday, March 29, 2024, at 12:00 AM UTC

Root cause: A recent update, intended to improve the reliability of Outlook on the web and Outlook mobile apps, contains a code configuration issue that's causing long running sessions, preventing attachment downloads and embedded image viewing.

Next update by: Monday, April 15, 2024, at 11:00 PM UTC

Title: Some users' outbound Exchange Online email messages may be marked as spam and not delivered

User impact: Users' outbound Exchange Online email messages may be marked as spam and not delivered.

More info: This isn’t connection method specific and thus occurs in all Exchange Online connection methods. Affected users receive a Non-Delivery Report (NDR) message that references the third-party anti-spam service name that has added the IP address to their block list.

Current status: We're working with the third-party anti-spam service to better identify the IP
address ranges affected by this problem, so that we can more quickly identify and manage sources of potentially malicious email messages. This will help reduce the frequency of spam and phishing email, which would also reduce the number of reported and blocked IP addresses, returning some mail flow as expected. In parallel, we're reviewing long-term solutions to prevent similar problems.

Scope of impact: The problem may impact some users sending outbound email messages if they're leveraging a specific third-party anti-spam service mentioned within the NDR.

Root cause: A third-party anti-spam service is blocking a portion of Microsoft’s email IP address ranges to protect organizations that use their services.

Next update by: Friday, March 8, 2024, at 9:00 PM UTC

Title: Some users may be intermittently unable to search for messages within Outlook on the web

User impact: Users may be intermittently unable to search for messages within Outlook on the web.

More info: Affected users may intermittently encounter an error message saying "Sorry, something went wrong. Please try again later."

Current status: Our targeted fix to address this configuration issue has begun deploying, and we expect that this should complete by our next scheduled communication update.

Scope of impact: Some users searching within Outlook on the web may be intermittently impacted.

Root cause: A latent configuration issue is causing a subset of infrastructure that facilitates search functionality to intermittently perform below our managed service threshold during periods of planned service updates, which is resulting in impact.

Next update by: Wednesday, February 7, 2024, at 2:00 AM UTC

Title: Some users may be unable to send or receive email messages and receive a Non-Delivery Report (NDR)

User impact: Users may be unable to send or receive email messages and receive a NDR with a 550 or 554 error code.

More info: This issue only occurs if either the sender or user who is receiving the message is utilizing a specific third-party anti-spam service. Senders receive the NDR which states that the message has been rejected due to a 550 or 554 error code and that their host IP address is listed on the third-party anti-spam service.

The error messages state "550 5.7.350 Remote server returned message detected as spam", "554 5.7.1 Service unavailable; Client host [xxx.xxx.xxx.xxx] blocked", or "‎550 5.7.1 This email was rejected because it violates our security policy."

Current status: We've deployed some anti-spam optimization changes and have seen positive results in terms of reduced counts related to delisted IPs. We're continuing to internally validate additional anti-spam optimization changes, as well as work in conjunction with the third-party service to delist IP addresses which are blocked on the third-party's anti-spam service.

Scope of impact: This issue may affect any user's mail flow if the recipient is leveraging a specific third-party anti-spam service to filter email messages.

Next update by: Thursday, January 18, 2024, at 7:30 PM UTC