- Check your mail settings
Make sure that your mail server settings, such as SMTP server, port number, username, and password are correct.
- Disable any anti-virus
Temporarily disable any anti-virus or firewall software and check whether you can send emails.
- Check attachment size
If you’re trying to attach large files to your message, the email provider might have restrictions in place. Try reducing the size of your attachments and check if this helps.