Title: Some users’ email with attachments sent from Outlook for Mac may be delivered without attachments
User impact: Users’ email with attachments sent from Outlook for Mac may have been delivered without attachments.
More info: Users could have verified if they’d encountered this problem in Outlook for Mac by reviewing their Sent Items to validate if a sent message contained an attachment. If users didn’t see the attachment, they could have replied to the message in their Sent Items folder to reattach and send the message again.
Final status: Our fix deployment has completed, and the issue is resolved. Affected users may need to update their Outlook for Mac client through the Apple app store or Microsoft store to receive the fix and remediate the issue for all users.
Scope of impact: This issue was specific to a very small percentage of users’ email with attachments sent from Outlook for Mac.
Start time: Monday, July 10, 2023, at 8:08 PM UTC
End time: Monday, January 22, 2024, at 9:05 PM UTC
Root cause: A conflict occurring with how our service detects attachment IDs before sending email in Outlook for Mac was resulting in the service removing attachments on sending email.
Next steps:
– We’re continuing to investigate the conflict to understand how it was introduced and better prevent similar future impact.
This is the final update for the event.
