Email Sync Problems

Fix Emails Intermittently Disappearing from a Shared Mailbox in Outlook

Maira Mehtab Sep 21, 2026 869 views

Question details

The user needs to resolve an issue where emails temporarily vanish and then return to an Outlook shared mailbox.

Product: Microsoft Outlook
Device & OS: not provided
Scenario: Managing and viewing emails within an organizational shared mailbox.
Observed behavior: Emails randomly disappear from the shared mailbox in both Outlook desktop and Outlook on the web, then reappear later, despite having recreated the local profile, repaired Microsoft 365, and checked rules.

Before you start

Verify that you have administrator access to the Microsoft 365 or Exchange Admin Center, as resetting shared mailbox permissions requires admin privileges.

Solution 1Recommended

Start Outlook in Safe Mode and Disable Add-ins

Running Outlook in Safe Mode bypasses third-party extensions, helping you determine if a conflicting add-in is causing emails to hide or sync improperly.

Sometimes third-party add-ins or integrations can conflict with Outlook's synchronization processes, causing emails to temporarily drop out of view.

Open the Run dialog

Press the Windows key + R on your keyboard to open the Run dialog box.

Launch Safe Mode

Type 'outlook.exe /safe' into the text box and press Enter to start Outlook in Safe Mode.

Monitor the mailbox

Observe the shared mailbox to see if emails stop disappearing. If the issue is resolved in Safe Mode, proceed to disable your add-ins.

Disable Add-ins

Go to File > Options > Add-ins. At the bottom of the window, select 'COM Add-ins' from the Manage drop-down and click 'Go'. Uncheck any suspicious or unnecessary add-ins, click OK, and restart Outlook normally.

Tip: If you are unsure which add-in is causing the issue, disable all of them first, then re-enable them one by one until the problem returns.

Solution 2

Remove and Reassign Shared Mailbox Permissions

Resetting the mailbox permissions forces the Exchange server to refresh your access rights, which can resolve persistent server-side synchronization glitches.

Solution 3

Update Windows and Microsoft Office

Keeping your operating system and Office suite updated ensures you have the latest software patches for known mailbox synchronization bugs.

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Frequently Asked Questions

Why are emails disappearing from both Outlook desktop and Outlook on the web?

When emails vanish across multiple platforms (both desktop and web), it usually indicates a server-side issue, conflicting server rules, or a mailbox permission error on the Exchange server rather than a local caching problem.

Can third-party add-ins affect shared mailboxes?

Yes, problematic or outdated Outlook add-ins can interfere with how emails are displayed and synchronized. Running Outlook in Safe Mode helps determine if an add-in is the root cause of hidden or moving messages.

How long does it take for shared mailbox permission changes to take effect?

After an administrator removes and reassigns permissions in the Exchange Admin Center, it can take anywhere from 15 minutes to a few hours for the changes to fully replicate across Microsoft 365 and reflect in the user's Outlook client.

Outlook & Email Problems