When selecting what credentials to use within your mail client, you have a choice between using either: mail.yourdomain.com or imap/smtp.yourdomain.com
There is no difference between using either of those options.
Primarily, we allow you to use mail.yourdomain.com so that you have a more customised experience and its easier to remember.
If you use mail.yourdomain it is likely you’ll get a “mail certificate name mismatch” / “cannot verify server identity” error. It’s nothing to worry about, this is because you are using mail.yourdomain.com so you can trust the certificate with the knowledge that the connection will remain encrypted. Once the certificate is trusted you should not receive any further warnings, unless the certificate changes.