Microsoft 365 Alert – Service Degradation – Exchange Online – Users may not see shared mailboxes appearing in the Outlook desktop client – RESOLVED

12/09/2023 08:04:00 AM (GMT)

NHSmail Reference : INC38209883

Microsoft Reference : EX674754

Issue Status : RESOLVED

Issue Description : Users may not see shared mailboxes appearing in the Outlook desktop client.

More info : Affected users may bypass the impact by using the Outlook on the web connection method or by manually adding the shared mailbox using the following instructions:

a. Open Outlook.
b. Choose the File tab in the ribbon.
c. Choose Account Settings, then select Account Settings from the menu.
d. Select the Email tab.
e. Make sure the correct account is highlighted, then choose Change.
f. Choose More Settings > Advanced > Add.
g. Type the shared email address, such as
h. Choose OK > OK.
i. Choose Next > Finish > Close.

Final Update : 12/09/2023 11:23:00 AM Microsoft confirmed deployment of the fix has successfully completed. Additionally, they have verified in their internal environments and received confirmation from some affected users that impact has been remediated.

Scope of impact : Any user may not be seeing previously available shared mailboxes in the Outlook desktop client.

Root cause : A recent service update, intended to resolve an unrelated issue, inadvertently caused a section of service infrastructure that facilitates the visibility of shared mailboxes to fail.

Next steps : Microsoft are reviewing their update procedures to understand why impact to shared mailboxes wasn’t caught during the testing phase. This will allow them to drive service improvements proactively, identifying similar issues in the future and improve their update procedures.

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