Routing of outgoing mail to dedicated TLS Mailserver for specific domains

Question

Hello all. I have a question that has been on my mind this week: Is it possible to route all outgoing mails destined for a certain domain to a dedicated mail gateway on the receipients side? (Every mail to *@abcd.com should be directed to tls.abcd.com). The receipient uses a separate mail gateway for TLS secured mail traffic. First I thought that an exchange sendconnector would be the logical way to do this, but I cannot go around the UTM since I want it to handle the forced TLS negotiation between the domains. So I see this task to be done on the UTM's side. Can anyone give me tip or even a nudge in the right direction where on the UTM I can accomplish this? Thanks in advance 
 Fabian

BAlfson · Answer

I see. My clients that have similar servers don't send faxes, but they don't relay web app emails off the SMTP Proxy, just that from their mail server(s). The SMTP Proxy should not be in Transparent mode except briefly for testing. 
 Instead of having the web app servers relay off the SMTP Proxy, just allow their emails out directly. Then, with split DNS, they can send directly to your fax gateway. Why wouldn't that work? 
 Cheers - Bob

BAlfson · Answer

Yeah, Doug, I probably should have responded to the TLS question in this thread and asked him to post the other question separately. 
 If you don't want to send emails to MTAs that can't communicate using TLS, drag the Any network object into 'Require TLS Negotiation Hosts/Nets' on the 'Advanced' tab of 'SMTP Proxy'. If you want to reject mail from senders that can't do TLS, put *.* into 'Require TLS Negotiation Sender Domains'. 
 Is that what you were trying to accomplish? 
 Cheers - Bob