Primary SMTP Changes after ADMT Migration of AD Connect Synced User.

Question

I'm doing User account migrations to a new forest with ADMT 3.2. We use Office365 for our mailboxes.

I do the migration by stopping ad connect moving accounts and hiding the old account in an unsynced OU. I have a non hybrid joined Exchange 2019 server installed into the new Forest. After migration the account connects back with the mailbox using the immutable id.

Weeks before we migrated I had changed the primary smtp addresses of the accounts to be that of the new email domain. After migration it appears the email address flips back to the old primary.

Initially this wasn't happening. After running set-remotemailbox against an account with no additional switches I could see in AD Connect where it would add the new Exchange servers legacyExchangeDN. At the same time it'd flip back to the old email address.

It seems after that and I change the primary email address back it works fine.

I'm trying to determine what is causing the flip flop of email addresses.

Answer 1

So far I've noticed it happens right after the delete of the user and as it is added back in the new domain. It has an older primary smtp. The values themselves seem to be there and haven't changed. Just the default (SMTP) address.

Maybe it somehow getting updated because of hybrid stuff but I doubt that.