Why do I see an SSL warning when connecting to my mailbox or sending emails with a mail client?

When you connect to your email through a mail client, or send emails, you are connecting to your domain through mail.your-domain.com.

Your SSL certificate is associated with the generic address (www.your-domain.com) and therefore brings up a warning when you connect to mail.your-domain.com.

Your connection will be successful, the SSL certificate will encrypt your connection, and you can ignore the warning.

However, if you want to prevent this warning from appearing, your mail client should have the option to accept the certificate permanently despite the warning.