This may be a really stupid question, but I can't seem to put my head around it. I have a mail server I'm trying to setup to service 6 domains. I will have multiple mail users accessing the server via POP3S or IMAPS.
Currently in MS Outlook, they are receiving an unverified SSL cert warning because I'm using a self-signed SSL certificate. I would like to purchase a SSL cert which would stop this warning from appearing.
Here is my question. I want each domain group to use something like mail.theirdomain.com as the incoming mail server name. Is there a way to do this without having to purchase a cert for each of the 6 domains? In other words, can I buy one for the mail.maindomain.com and have it authenticate the other DNS names?
Currently in DNS, the mail.theirdomain.com has a CNAME setup to mail.maindomain.com. I'm running Dovecot for incoming and Sendmail for outgoing. Latest version on Debian 6.