Why not set up a gapps email. Its free up to 10 addresses and you can set it to your domain. That should solve your issue of email address being different domain name.

You can find the free version here

http://www.google.com/apps/intl/en/group/index.html

If you switched to gapps now, all you need to do is set the mx records to google for that domain. Google will need to verify you own the domain by either uploading an html file or set a cname and it works. Check this out

http://www.likoma.com/using-google-apps-and-gmail-for-youyourdomaincom/