Although there is no automated way to do this at this point you can have an SPF record added to your account by contacting WH support.
An SPF record can help combat spam. To find out more about it check out thier site:
http://spf.pobox.com/ There is an ongoing discussion on the topic at the WH fourms here:
http://forums.westhost.com/showthread.php?t=7322At this time you can only implement Step One of this which is adding the record to your account but some users have reported that it has helped quite a bit on bounce back emails from spam that was not sent out by them but trying to look like it was sent from thier domain. WH is looking into being able to check SPF records for incomeing mail or at least making it an option.