postfix transport maps

I am curious if someone can help me solve this problem with the turnkeylinux lamp build.. I am trying to setup a transport map so that I can use my lamp build to traffic email for a domain.

for instance.. send all mail from

*@domainname.com smtp:mx1.arealmailserver.com
and/or
user@domainname.com smtp:mx1.arealmailserver.com

I cant figure out the correct way to set this up. :)

Thanks