Background: We will be using Exchange 2010 to deliver time-sensitive email alerts to known users outside of our organization (lets call our org 'internal.loc').
The project calls for some sort of failover capability but without the use of MS Clustering services.
We have two Windows Server 2008 Standard machines. Exchange is installed on both and both are configured as Hub Trasnports. Let's call these two machines EXCH-A and EXCH-B.
The email alerts will be generated by our own custom business application. We also have another domain (let's call it alerts.foo) which will act as the sender of the alerts and the recipient of return email.
So here's a basic diagram of the mail flow:
Biz App > EXCH-A > SMTP-A > TO: email@example.com FROM: firstname.lastname@example.org
If EXCH-A fails, then we have EXCH-B on standby. Our biz app would first poll EXCH-A for a heartbeat. If there's no activity then our biz app would use EXCH-B to deliver the alerts.
Here a more specific description of the mail flow:
1) Biz App checks EXCH-A health.
2) If EXCH-A ok then proceed to use SMTP-A to deliver TO: email@example.com FROM: firstname.lastname@example.org.
3) If EXCH-A is unavailable then use EXCH-B/SMPT-B to deliver to email@example.com.
QUESTION: How do we handle the return email? Specifically in regards to Mailbox setup and DC/AD configuration.
Assume both EXCH-A and EXCH-B have mailboxes and assuming we have one internal user - firstname.lastname@example.org - acting as the sender and the recipient for return email.
With one machine, it's a more or less a vanilla setup. With two machines (in our poor-mans failover setup) how would we route return mail if EXCH-A is not available. Is it possible to setup up two discreet mailboxes for the user email@example.com, one on each machine? Or perhaps the two mailboxes should be "synced"?
Would be grateful for any help and, of course, I'll be happy to elaborate as needed.