Masquerading, Sendmail, Multiple Domains

[Corey Head]

Hello!

I'm running sendmail successfully, but occasionally
some emails will not go through to some ISPs because
they get marked as spam.  My guess is it's because I
have multiple domains hosted on the same server.  So,
the email would appear to come from domain1.com, but
the return address is domain7.com.  I've found yahoo,
earthlink and comcast will deny those messages
sometimes without specific user intervention.  

Is there a way with Masquerading that I can setup
specific users for each specific domain?  In other
words
domain 1:  user1-1, user1-2, user1-3 (each receiving
different mail)
domain 2:  user2-1, user2-2, user2-3 (each receiving
different mail)
In some ways it's like virtual hosting in
apache...from the outside you can't really tell what
server you're on/coming from with the various domains.

I currently have some catch-all accounts, but would
like to have more than one user be able to
receive/send mail from a particular domain.

Thanks!
Corey

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