If you're just after high uptimes for your email server, and your email server doesn't need to be anything more than an email server, and you already happen to

If you're just after high uptimes for your email server, and your email server doesn't need to be anything more than an email server, and you already happen to have a need for a Unix server and a qualified Unix admin, then sure. Typical companies, though, are mostly Windows shops and really are looking to get something more along the lines of an integrated communication/collaboration/scheduling tool like Microsoft Exchange or GMail.