User impact: Users may have intermittently been unable to “Reply All” to email messages using a group mailbox in Outlook on the web.

More info: Affected users intermittently received the following error message when attempting to “Reply All” from a group mailbox in Outlook on the web: “This message can’t be sent right now. Please try again later. Set action is invalid for property.”

The impact was able to be bypassed by replying to these messages from outside of a group mailbox.

Final status: Following our additional testing with affected users, we’ve confirmed that our revert of the offending code change has successfully remediated the impact.

Scope of impact: This event may have intermittently impacted users who attempted to “Reply All” to email messages using a group mailbox in Outlook on the web.

Start time: Friday, August 4, 2023, at 5:32 PM UTC

End time: Tuesday, October 3, 2023, at 6:00 PM UTC

Root cause: A code change meant to improve conversation grouping was causing the intermittent “Reply All” impact.

Next steps:
– We’re further analyzing the offending change so we can help identify similar issues during our validation and testing periods and before they can result in impact.

This is the final update for this event.