No, that is not an option. If you want to use
mail.mydomain.com as the server name, then when you set the server up use
mail.mydomain.com rather than
But wait, you are talking about multiple domains, right? Mail-in-a-Box wasn’t really created to be concerned with vanity. Traditionally, mail servers served email for multiple domains, and people dis not worry about what the MX record was. The MX record was what it was. Then cPanel changed all of that.
My best suggestion to you is to use a neutral domain name for the mail server. Maybe something like
Or, you can be the guinea pig. Try adding a email account for
mail.domain.com for a few domains, then test. I know this works well for webmail access, but I imaging that it will fail miserably as the SSL certificate used by dovecot will be the main server certificate. So no, I don’t think you can actually do what you want with MiaB.
Bottom line: Probably not as dovecot will be using the server’s SSL certificate.