After some searching I've come up totally empty handed on if there is any standard (or non-standard for that matter) specification or best practice for specifying the IMAP server for a domain name. I.e. if I have an account such as "firstname.lastname@example.org", and I wish to read my mail via IMAP, is there any DNS record which would indicate to my mail client which mail server it should be contacting? I've never seen anything like this, and virtually all email setup instructions I've seen include an exact host name for IMAP, e.g. "mail.example.com" or "imap.example.com". I guess the assumption is that the employees or other users of example.com can find out what server to use from their administrator. However if example.com were to have thousands of accounts, this would become burdensome. It would seem very useful to just enter your email address "email@example.com" and have it look up the IMAP server name in DNS based on the email's domain name (not dissimilar to how an MX record works for SMTP).
Anyone heard of anything like this?