SmarterMail split domain with Exchange server (both servers sharing the same SMTP domain)
Question asked by Ionel Aurelian Rau - 3/10/2022 at 8:25 AM

Is is possible to configure a split domain scenario with SmarterMail and MS Exchange server? We have already set it up with Exchange as the primary point of entry for email and Exchange will deliver emails locally for the users that exist on the Exchange Server and to the SmarterMail server for the rest of the users it does not find locally. All mailboxes share the same SMTP domain.

So, this works:
1. Email comes in for user1@example.com from the Internet
2. Exchanges finds the user locally -> it delivers the email directly to the mailbox

1. Email comes in for user2@example.com from the Internet
2. Exchange does not find a mailbox for this user
3. Exchange forwards the email to SmarterMail server which delivers it to user2@example.com as that is local to SM

1. user1@example.com (on Exchange server) sends email to user2@example.com 
2. Exchange does not find a mailbox for this user
3. Exchange forwards the email to SmarterMail server which delivers it to user2@example.com as that is local to SM 

Now, the problem is that if user2@example.com tries to send email to user1@example.com, that is not possible as SmarterMail will complain that the mailbox does not exist.

How can we achieve a setup where user2@example.com (local to SmarterMail server) can also send email to user1@example.com  (local to Exchange Server)?

Thank you!

3 Replies

Reply to Thread
Zach Sylvester Replied
Employee Post Marked As Answer

Thank you for reaching out to the community. We actually have a setting that is perfect for this. 
In the domain configuration, you can set inbound message delivery to External use MX record and then turn on Deliver locally if the user exists. This should make it so when user2@example.com(On SmarterMail) tries to send to user1@example.com(On Exchange) it will check locally then if the user doesn't exist it will send it out to the exchange server using the MX record. 

Please let me know if this helps. 

Kind Regards, 
Zach Sylvester
Technical Support Specialist
SmarterTools Inc.
(877) 357-6278
Ionel Aurelian Rau Replied
Thank you very much - this did the trick! Now users on the SmarterMail server can send email to those on the Exchange server.

Stefano Replied
I suggest you to use External (use host address) rather than MX, I've had some problems with MX settings.

Reply to Thread