Microsoft 365 Alert – Service Degradation – Exchange Online – Users may intermittently be unable to “Reply All” to email messages using a group mailbox in Outlook on the web – RESOLVED

15/09/2023 11:47:00 AM (GMT)

NHSmail Reference : INC38279595

Microsoft Reference : EX673361

Issue Status : RESOLVED

Issue Description : Users may intermittently be unable to “Reply All” to email messages using a group mailbox in Outlook on the web.

More info : Affected users intermittently receive 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 can be bypassed by replying to these messages from outside of a group mailbox.

Final Update : 04/10/2023 09:32:00 AM – Following Microsoft’s additional testing with affected users, they’ve confirmed that their revert of the offending code change has successfully remediated the impact.

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

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

Next steps : Microsoft are further analyzing the offending change so they can help identify similar issues during their validation and testing periods and before they can result in impact.