Networks

Org. uses ISP to host email domain. All mail leaving Org. sent via SMTP Virtual Server to smart host @ISP with authentication. Incoming mail popped from ISP with pop3 connector then routed to mailboxes. Two recipients receive Domain email off site,no mailbox @ Org. Users wish to send or selectively forward email to off site recipients. Problem: exchange won't send email with Org's external SMTP Address off site. Off site recipients have been configured as ADUC Contacts with internal smtp add.,external smpt add.,both and only X400.
Exchange needs to recognize these two specific SMPT addresses as needing to be forwarded to the smart host, but havn't been able to figure out how. I'm working with a legacy situation with high level resistance to change. Any Ideas?