We have an issue that I believe Route-By-Sender may be able to help with, but I can’t seem to find where to get it. If I recall it was an add-on I needed to purchase, but where do I purchase it and what is the cost?

The problem I have is, one of our domains is moving from our Exchange server to Google Workspace.  But as their mail database is so big, they cannot move the old emails easily.  So they will maintain the old email on our exchange server and process all new emails through their new Google mailboxes. 

In general, this this is working fine, however the problem is, if any of my team send an email to them, it goes to the internal mailbox, not the new Google one.  As I understand it, Exchange will always route emails for local domains internally, even if a send connector exists.  But I believe your Route by Sender can force inter domain emails to go via a smart host, which would be perfect for us. 

We will only need it for a few months, until the slowly migrate all their existing emails over to Google, so providing the Route by Sender option is not too expensive, it will resolve our problem.