Shared Mailbox Not Showing in Outlook? How to Fix It

Your admin says you've been given access to the info@ or accounts@ shared mailbox, but it simply isn't there in Outlook. Or it appears, but clicking it gives "Cannot expand the folder. The set of folders cannot be opened" or "You do not have permission to perform this action". Sometimes it works in Outlook on the web but not on your PC, or it shows in classic Outlook and vanishes when you switch to the new Outlook.

Shared mailboxes are essential for small teams, so this gets frustrating quickly. The cause is usually timing, how permission was granted, or which version of Outlook you're using.

Why This Happens

In Microsoft 365, giving someone Full Access to a shared mailbox normally triggers automapping, which makes the mailbox appear in classic Outlook by itself. But:

• Permissions take time to apply. It can take up to an hour, occasionally longer, for new access to show up.
• Automapping only works for direct permissions. If access was given to a security group rather than to you individually, Outlook won't add the mailbox automatically.
• Automapping may be turned off for that permission, often deliberately in businesses with lots of shared mailboxes.
• New Outlook and Outlook on the web don't use automapping in the same way. You add shared mailboxes yourself.
• The wrong permission was granted. Send As or Send on Behalf lets you send from the mailbox but doesn't let you open it. You need Full Access to read it.

Fix 1: Wait, Then Restart Outlook Properly

If access was granted in the last hour, give it time. Then close Outlook completely, check it's not still running in the system tray or Task Manager, and reopen it. Test in Outlook on the web at outlook.office.com: if the mailbox can be opened there, your permissions are fine and the problem is the desktop app.

Fix 2: Add It in the New Outlook or Outlook on the Web

1. In the folder pane, right-click Shared with me or your own mailbox name. Look for an option such as Add shared folder or mailbox.
2. Type the shared mailbox name or address and choose Add.
3. The mailbox appears under Shared with me. Expand it to see its folders.

Fix 3: Add It Manually in Classic Outlook

1. Go to File > Account Settings > Account Settings.
2. Select your own Microsoft 365 account and click Change.
3. Click More Settings, then the Advanced tab.
4. Under Open these additional mailboxes, click Add, type the shared mailbox name and click OK.
5. Click Apply, then OK, Next and Finish. Restart Outlook.

Fix 4: Sending From the Shared Mailbox

To send as the shared mailbox, show the From field in a new email (in classic Outlook, Options > From; in the new Outlook, look for From under the message options), then choose Other email address and type the shared address. If you get an error saying you don't have permission to send as this user, you need Send As permission, which your admin grants separately. Once you've used it once, Outlook remembers it in the dropdown.

Fix 5: Sent Items Going to the Wrong Place

By default, emails you send from a shared mailbox are saved in your own Sent Items, not the shared one. That's why colleagues can't see what's been replied to. It's a mailbox setting, so your admin needs to fix it (see below).

For Your Microsoft 365 Admin

Check and grant permissions. In the Microsoft 365 admin centre, go to Teams & groups > Shared mailboxes, select the mailbox and edit its members or permissions. In the Exchange admin centre, look under Recipients > Mailboxes, select the mailbox and open Delegation to see Read and manage (Full Access), Send as and Send on behalf.

In Exchange Online PowerShell:

• Check: Get-MailboxPermission -Identity info@yourdomain.co.uk
• Grant with automapping: Add-MailboxPermission -Identity info@yourdomain.co.uk -User jane@yourdomain.co.uk -AccessRights FullAccess -AutoMapping $true
• Grant Send As: Add-RecipientPermission -Identity info@yourdomain.co.uk -Trustee jane@yourdomain.co.uk -AccessRights SendAs

To stop automapping for someone (for example, if Outlook is slow with too many mailboxes), remove the permission and add it back with -AutoMapping $false. The user then adds the mailbox manually.

Save sent items to the shared mailbox:

Set-Mailbox info@yourdomain.co.uk -MessageCopyForSentAsEnabled $true -MessageCopyForSendOnBehalfEnabled $true

Remember that a shared mailbox doesn't need a licence up to 50 GB, but it does if it needs more storage or an archive, and shared mailboxes shouldn't be signed in to directly.

How to Stop It Happening Again

Most shared mailbox problems come from ad hoc permissions: granted to some people directly, others via groups, with automapping on for some and off for others. A documented approach, where access is granted consistently as part of a proper joiner and leaver process, means new starters see the right mailboxes on day one and leavers lose access straight away. Our Microsoft 365 setup guide covers how to structure this.

When to Call in Help

If shared mailboxes keep disappearing, Outlook gets slow with them, or you need permissions tidying across the business, our IT support team can sort it remotely. With our managed IT service, joiner and leaver access is handled for you. Get in touch.

Related Reading

• Outlook Keeps Asking for Password? How to Fix It
• Outlook Search Not Working? How to Fix It
• Microsoft 365 Setup Guide for Small Teams