A shared mailbox or calendar disappeared from Outlook
Outlook should auto-mount shared mailboxes based on Microsoft 365 permissions. If it is gone, usually the assignment expired or did not sync.
Try this first
- 1Fully close Outlook and reopen. A new session re-fetches shared mailboxes (can take up to an hour).
- 2Outlook Web (outlook.office.com): is the shared mailbox there? Then the local Outlook cache is the issue.
- 3Ask IT whether the assignment in Microsoft 365 is still active; accidental removal happens more than you would think.
- 4If manual add works (File > Account Settings > More Settings > Advanced > Add) but the automatic does not, it is cache. Rebuilding the Outlook profile fixes it.
When to bring us in
If multiple colleagues lose it at once, or a shared calendar vanishes everywhere, it is a tenant setting. Five minutes of work in Exchange admin.
See also
- Outlook crashes or freezes on large attachmentsUsually the mailbox cache is the culprit, not Outlook itself. Shrinking or relocating usually helps within ten minutes.
- Teams: they cannot hear me, or I hear nothingIn our experience Teams usually picked the wrong audio device after a Windows update or a new headset.
- OneDrive has stopped syncingThe cloud icon is grey or has a warning. Locally changed files are not showing up for colleagues.
None of the above fits?
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