Outlook Not Receiving Emails — How to Diagnose It Properly
Outlook sending fine but nothing coming in? Walk through the same checks a support engineer runs — mailbox, rules, cache, then the mail server itself.
Part of our IT advice UK hub — plain-English answers from Microsoft-certified engineers.
Symptoms
- Sent items go out but the inbox is quiet for hours
- Webmail (outlook.com or OWA) shows messages Outlook doesn't
- Some senders come through, others never appear
Likely causes
- A misfiring inbox rule silently moving mail to a subfolder or deleted items
- The Outlook profile / OST file is corrupted
- Cached Exchange Mode is out of sync
- The mailbox is full or the sender is blocked at the tenant level
Step-by-step fix
- 1
Check webmail first
Sign in to outlook.com or your organisation's OWA. If the message is there but not in Outlook, it's a client problem. If it's not in webmail either, it's a mail-server or sender problem.
- 2
Rules and Junk
File → Manage Rules & Alerts. Disable every rule, then send yourself a test. Also check the Junk folder and the Blocked Senders list — genuine mail ends up there more often than people admit.
- 3
Rebuild the OST cache
Close Outlook. Delete the .ost file for your profile (Windows: %LOCALAPPDATA%\Microsoft\Outlook). Reopen — Outlook rebuilds from the server. Nothing is lost because the mailbox lives on Exchange, not the OST.
- 4
Repair the Outlook profile
Control Panel → Mail (32-bit) → Show Profiles → add a new profile, set it default. If the new profile receives mail, the old one is corrupt — leave it archived, use the new one.
- 5
Check mailbox quota and tenant blocks
In OWA, Settings → General → Storage. If you're at 99%, mail is bouncing. For business tenants, the admin should check the Message Trace in Exchange Admin Center — it says exactly why a message did or didn't arrive.
Watch out for
- Do not run scanpst.exe on a modern Exchange OST file — it's for PST archives only and can make things worse.
Frequently asked
Why does it work on my phone but not on Outlook?▾
The phone talks to the server directly over IMAP or Exchange ActiveSync. If it's fine there, the mail's arriving — Outlook's local cache is the problem.
Can I lose emails by deleting the OST?▾
No, provided the account is an Exchange, M365 or IMAP mailbox — everything lives on the server. Only pure POP3 accounts store mail locally, and those are increasingly rare.
Still stuck? A UK engineer can jump on remotely.
Fixed fee, secure one-time session, usually within the hour.