I also tested this as I use spamexperts I have a other mx record then the default one while I did try the srv and cnames I still get imap.domain and the wrong mx as autodiscover with Emclient.
I know emclient uses the autodiscover.tcp but then I get autodiscover.domain but the certificate is on mail.domain of course I can't get that with autodiscover with emclient on pc atleast.
Outlook seem to remember something.
Eventually I get imap.domain and smtp.domain strange with emclient strange.
Can we not add a autodiscover file to our server or do we need Enhance to add something for that?