Outlook not sending or receiving email

1. Check the internet and Work Offline

Open a website in your browser to confirm the internet works. Then look at the bottom bar in Outlook. If it says "Working Offline" or "Disconnected", go to the Send/Receive tab and click "Work Offline". If the button looks shaded, you are offline. One click reconnects you.

2. Look for a stuck message in the Outbox

Mail that fails to send waits in the Outbox. Open that folder. If a message has a big attachment (most providers cap it at 20-25 MB), delete the message, shrink the files or share them as a cloud link instead. One stuck message blocks everything behind it. Clear it and the rest will go.

3. Your mailbox may be full

When the quota is full, new mail stops arriving and sending can fail too. Check usage under File > Info > Mailbox Cleanup. Empty "Deleted Items" and "Junk Email", then delete or archive old messages with large attachments. Your provider sets the limit.

4. Review your Send/Receive settings

On the Send/Receive tab, click "Send/Receive All Folders" (F9). If mail still does not arrive, open Send/Receive Groups > Define Send/Receive Groups. Check that your account is listed and that "Include this group in send/receive (F9)" is ticked for "All Accounts".

5. Sign in again if the password changed

If you changed your mail password elsewhere, Outlook keeps trying the old one and stalls. Enter the new password when prompted. If no prompt appears, go to File > Account Settings > Account Settings, select the account and click "Repair". The wizard rebuilds the connection.

With 2-step verification on, providers such as Gmail and Yahoo often want an "app password" instead of your normal password for older-style sign-ins. Create one on your account's security page and type it into Outlook as the password. Microsoft 365 and Outlook.com accounts use modern authentication. A browser-style sign-in window opens and you log in there.

6. New Outlook or classic Outlook?

Windows can have two versions. Classic Outlook (outlook.exe) is the older desktop program. New Outlook is the web-based app with a "New Outlook" switch at the top right. Their settings differ. The File > Account Settings path above is for classic. In New Outlook, open Settings (the gear) > Accounts. If the trouble started after switching, turning the switch off and returning to classic is a handy workaround.

7. Start in safe mode

Press Windows key + R, type outlook.exe /safe and click OK. If everything works in safe mode, an add-in is the culprit. Go to File > Options > Add-ins > Go and turn add-ins off one at a time to find it.

8. Create a new profile

Open Control Panel, choose "Mail (Microsoft Outlook)" > "Show Profiles" > Add. Add your account to the new profile and select "Always use this profile". This ends most damaged-profile problems. Mail stored on the server is not lost. If you keep local archives in .pst files on the computer, back them up first.

9. IMAP, POP and SMTP basics

Incoming mail uses IMAP or POP. Outgoing mail uses SMTP. IMAP keeps messages on the server, while POP downloads them. Only your e-mail provider can give you the right server names, ports and encryption type, so ask them. Typical examples are 993 (SSL/TLS) for IMAP and 587 (STARTTLS) for sending. If your provider lists different values, use theirs.

10. On Microsoft 365, ask your admin

On a work account, the licence may have expired, the user may be blocked or the mailbox may be full. An admin can check this in the Microsoft 365 admin center under Users > Active users. The Service health page shows any outage.