can you set up a domain so that a user on this domain could set up his email client software with mail server addresses of domain.com, mail.domain.com, pop.domain.com, or smtp.domain.com all interchangeably? if this would work, what DNS and raq site settings would you use to accomplish this?

I suppose. You'd have to set up CNAMES for each, pointing to the server IP address. I'm not sure why you'd want to do this, but so long as it hits the server, you'd be fine.

I would think however, you'd only want to MX *one* of these to actaully handle the incoming mail.

one is all i have now, but at least adding mail.domain.com would save me from having to have all of my customers who came over with me to the new server from having to reconfigure their mail server addresses to just domain.com. they were all set up previously as mail.domain.com.

when would you use 'CNAME' instead of 'A RECORD'? this is a general question, but it sounds like you might know the answer to it off the top of your head.

This is how I'd do it...

Wildcard the domain so that *anything*.domain.com hits the server IP address. That way, they can have *anything* before their domain and it will work.

If you don't want to do that, then I'd set a CNAME for mail, going to *servername*.

*servername* should be whatever the name of the server is of course.

how do you wild card it? do i just put an '*' in that field or something else?

Gnererally just an * yes, and then point the * to the server IP address.