Add Safe Senders' Domains to Exchange 2010

I did a search on this and could not find an answer.

We have emails getting bounced by the content filter in Exchange 2010, and some of those emails are from vendors.  When I say bounced, they are getting rejected and returned to sender by Exchange Server 2010, not just ending up in the Junk Mail folder.  I would like to add their domains to a safe sender list, so the content filter does not bounce them.

Thanks!

Michael