While performing a hybrid Office 365 migration for a client, I found that newly migrated users were getting their primary SMTP addresses changed. This organization uses %firstname.lastname@example.org in their email address policy to stamp users with email@example.com. Their UPN logins however, are firstname.lastname@example.org.
After migrating, users still had all of their proxy addresses properly assigned, however their primary SMTP address had changed to their UPN alias. Not good.
It took some digging around, but I discovered that a low priority email address policy was the culprit. For reasons I have yet to determine, even though testing users with a priority 1 policy to specifically stamp using the proper SMTP address, this low priority policy was over-riding.
Fortunately in my case, the customer was fine with a quick modification to the offending policy and things are working fine now.
So if you see this happening, here are a couple of quick steps to see:
From Exchange powershell (on prem) type:
Get-remotemailbox <offending userid> | fl policiesincluded
This will output the GUID of the email address policy applied to this user.
Once you have the GUID, you can use this command to locate the GUIDs of your email address policies:
Get-emailaddresspolicy –idendity “EmailPolicy” | fl GUID
Where “emailpolicy” is the name of each of your policies.
You can then match the GUIDs, then modify your offending email address policy to properly stamp the remotemailbox objects.
Joe Hanning, PEI