Mail for domain issue

[Greg Harris]

Hello all,   I am running Postfix 2.1.5 and Cyrus 2.1.15 on a RHEL3 clone and using MySQL on the back end.  Everything works beautifully and as expected.  The only issue I am trying to figure out does not seem to be listed on any list or Googlized search.  I am trying to get mail to go to domain.com along with mail.domain.com.  The mail.domain.com works great.  Any time I send a mail to domain.com, I get a permanent 550 error.  I guess this is to be expected, since it would be seen as a different domain, but how do I make it receive on both domains?  I know this has to be something simple and is probably documented somewhere, but I can’t seem to come up with the correct terminology.   Thanks for the help,   Greg Harris