A lot of our customers are using Google Business Applications. To find out more about configuring your email client to work with Google Business Apps, visit this site: http://mail.google.com/support/bin/answer.py?hl=en&answer=12103
When following the instructions, please note that you must replace gmail.com with your domain name in all places EXCEPT for the incoming and outgoing server settings.
For example:
Username: your_name@your_domain.com
Password: **********
Incoming Mail Server: pop.gmail.com
Outgoing Mail Server: smtp:gmail.com