Here are some tips to help troubleshoot email delivery problems on your computer:

1. Check your internet connection.
2. Check account settings in the email application.
3. Restart the email application.
4. Check for any suspicious activity from unauthorized devices.
5. Run a basic virus scan and malware scan on your computer.
6. Make sure necessary ports are open.
7. Check for any external blocks to your services.
8. Speak to your ISP and find out if they are experiencing any issues.