I beleive you could leave your current qmail server as-is, besides just telling to to send all outgoing email over to the approved server.
To do this use an smtproutes file in the qmail control directory.
Example smtproutes entries:
domain_you_want_to_route:primary-server.domain.com
another_domain_you_want_to_route:another-server.domain.com
If you want to route all mail and then you should have the line like:
:primary-server.domain.com
After you have done this restart your qmail server for the changes to be noticed.
I hope that helps!
Sam
