First: check webmail
Sign in to Outlook on the web — for Microsoft 365 that is outlook.office.com; on hosted Exchange it is your provider’s webmail address. Look for one of the missing messages.
- It is in webmail: your mailbox is fine and the Outlook app is not syncing. Go to fixes 6 to 9.
- It is not in webmail either: the message did not reach your inbox. Start at fix 1.
1. Look in Junk and the Other tab
Check Junk Email, and if your inbox is split into Focused and Other, check Other. If you find the message there, mark it Not junk or move it to Focused so the next one arrives where you expect.
2. Check for a filter or a changed view
A filter on the message list — unread only, flagged only, or a date range — makes mail look missing. Clear any filter, and sort by date received, newest first.
3. Check your rules — and look for ones you did not make
Rules can move incoming mail into another folder, delete it or forward it elsewhere. Open your rules (in classic Outlook: File → Manage Rules & Alerts; in the new Outlook and on the web: Settings → Mail → Rules) and check each one. A rule you do not recognise that moves, deletes or forwards mail is a classic sign of a hacked account — criminals use them to hide replies while they impersonate you. Delete it, change your password, and tell your IT provider.
4. Check blocked senders and quarantine
Look at your Blocked senders list in the junk mail settings. Your organisation’s spam filter may also hold suspicious messages in quarantine before they reach any folder; your IT administrator or email provider can check and release them.
5. Check your mailbox is not full
A full mailbox rejects incoming mail and senders get a bounce. Our guide to fixing a full mailbox explains the warning stages and how to free space quickly.
6. Make sure Outlook is not working offline
In classic Outlook, look at the status bar at the bottom of the window. If it says Working Offline or Disconnected, go to the Send / Receive tab and select Work Offline to turn it off. Then press F9 to send and receive.
7. Check the connection and restart Outlook
Close Outlook completely, check the computer is online, and open it again. If the status bar shows a password prompt or “Need password”, sign in — our guide on Outlook asking for a password covers repeated prompts.
8. Update the folder or rebuild the cache
In classic Outlook, select the folder and choose Update Folder on the Send / Receive tab. If folders still do not match webmail, the local copy of your mailbox may be damaged: create a new Outlook profile (Control Panel → Mail → Show Profiles → Add) and let it download a fresh copy. Your mail is safe on the server while you do this.
9. Update Outlook
Install outstanding Office and Windows updates and restart. Sync bugs are regularly fixed in updates.
10. If the message never arrived: follow the trail
- Ask the sender for their bounce message (non-delivery report). It says exactly why the message was refused — a full mailbox, an unknown address or a blocked server.
- If nobody in the business is receiving email, check where your domain’s mail goes with our MX lookup. A recent DNS change, a move between providers or an expired domain name are the usual causes.
- If only some senders are missing, your provider can trace the message through its logs if you give them the sender’s address and roughly when it was sent.
When to call for help
If webmail is missing mail too and none of the checks above explain it, it is a job for whoever runs your email: they can see the delivery logs you cannot. If that is us, ring the support line and we will trace it while you are on the phone.