Why doesn't Mail.app ver. 4 recognize Google Apps accounts as Gmail IMAP
The Gmail IMAP accounts are there for convenience: Gmail is popular and the possible in &amp; out servers are the same for the lot of users. Having ugly technical data filled upfront makes the user experience more laid back and minimizes the possibility of typoing wrong data.



The domain itself doesn't tell if it is a Google Apps domain or not. Yes, (any) mail software could try to retrieve the info through some channels, but that would lead to extra traffic. Also using your domain with Google Apps is rather marginal versus not using your own domain with Google Apps. 

Furthermore, it would be rather dubious if Apple tried to check every non-gmail.com domain if it is a Google Apps domain or not. Every query leaves a footprint.