Hi Exchange Guru!
I'm on the front of a problem with mail sending. Here are the context and explanation.

* I have a SBS server that manage a email domain (domain.be)
* A new user from US come with his domain.com email
To give him the ability to to connect and send email thrue exchange I have add a new smtp domain (domain.com)
* Synchronisation is made without anny trouble using RPC

The problem is:
the server that manage domain.com is not mine thus I cannot change anything on.
This server need authentication to receive mail from user@domain.com to user@domain.com
I suppose this security settings has been made to avoid spam.

Anyway, when my new user send email to his collegue (so from us_user@domain.com to collegue@domain.com), he receive an error:
"5.1.0 - Unknown address error 554-'<us_user@domain.com>: Sender address rejected: Access denied'"

I suppose this is normal cause Exchange send the mail using dnslookup and try to post it directly on the remote smtp without authentication.

So the question is:

Is there a way/trick to send email to domain.com using authentication only for us_user@domain.com to avoid this problem?

I have already try to do it using a new smtp connector but it seems to catch all the mail for the remote domain.com, so the usual SBS users pass thrue this connector too and I don't want, I just need this trick only for us_user@domain.com

Has anyone a solution or another way to think???

Regards