Outlook not sending or receiving mail is one of the most common support requests we get. Work through these checks roughly in order — most issues get resolved in the first three.

1. Check you're not in Work Offline mode. Click the Send/Receive tab — if Work Offline is highlighted, click it to turn it off.
2. Check your internet connection. Try loading a website or another app that needs the internet to confirm you're actually online.
3. Look for a stuck message in the Outbox. A single oversized attachment or bad address can jam every message behind it. Open the Outbox, and if a message is stuck, drag it to Drafts, remove any large attachment, and resend.
4. Restart Outlook, then restart your computer. This clears up more connection issues than people expect.
5. Check for an outage. If you're on Microsoft 365, check the Microsoft 365 Service Health page (your admin can also check this) — sometimes the problem isn't on your end at all.
6. Confirm your mailbox isn't full. On POP/IMAP accounts, check available storage; on Exchange/Microsoft 365, check your mailbox quota in the admin center.
7. Run a Quick Repair. Go to Control Panel > Programs > Programs and Features, select Microsoft Office, click Change, then Quick Repair. If that doesn't help, run Online Repair instead (it takes longer but fixes more).
8. Rebuild your Outlook profile. Corrupted profiles are a common root cause. In Control Panel, search for Mail, click Show Profiles, and create a new profile, then set it as the default and re-add your account.

Common Questions

Outlook on the web works fine, but desktop doesn't — what does that mean?

It means the problem is local to your computer or your Outlook profile, not your mailbox or the server. Focus on steps 3, 4, 7, and 8 above.

I keep getting "Cannot connect to server" — what should I check first?

Check your internet connection first, then confirm Work Offline is switched off. If both look fine, the account's server settings may have changed (common after a password reset or an IT migration) — an Office repair or a fresh profile usually resolves it.

Should I repair Office or just rebuild my profile?

Try the Quick Repair first since it's fast and non-destructive. If the problem persists after that, rebuilding the profile is the next step — it's more likely to fix account-specific sync issues that a repair won't touch.