Our company was acquired by a larger organization and we have migrated all of our user mailboxes to their Office365 tenant and in the process changed primary SMTP to their domain. We have an on-premises Exchange system, which is currently used to handle some shared mailbox and SMTP relay for applications in our data center under the former accepted domains. User mail sent to the former accepted domains are routed to the O365 destination mailbox via contacts or Mail-enabled Users. The on-premises Exchange server is version 2010, which is out of support and my organization would like to turn it off.
I am tasked with turning off the on-premises Exchange system. I originally planned to do this after the former domains are configured to point to Office365 and mail flow for the former domains no longer goes through my data center or the on-premises Exchange server. However, there is some need to keep the former domains on-premises, to be used for outgoing SMTP only. The organization is averse to purchasing an updated Exchange License to handle such a task.
Would Mail-in-a-Box be able to replace the Exchange Server’s functionality and direct mail sent to users on one of the former domains to the new destination mailboxes?