Change UPN, Primary SMTP in a Exchange Hybrid

Question

Hi,

I have a requirement to change UPN and primary email addresses of all users in to a new one in a Exchange Hybrid deployment. Due to few mailboxes they need to retain in on-prem for sometime, "autodiscover" record is still points to on-premises servers.

I need to figure out the steps I should take to perform this change smoothly.

1. Add "bsb.com" UPN Suffix -Active Directory Domain Trusts
2. Add "bsb.com" as an accepted domain in Exchange On-prem Add "bsb.com" SSL in Exchange On-Prem
3. Add/ Verify "bsb.com" in M365 tenant.
4. Add "autodiscover" record for "bsb.com" pointing Exchange On-prem
5. Change UPN/Primary SMTP of all Synchronized Users
6. Run Hybrid Configuration Wizard
7. Verify functionality

Appreciate it if you could share your thoughts or suggestions on above, especially if any of you have undergone a similar change.

Regards,

Kavindu

Answer 1

Hello @Kavindu Dayananda

This looks like a good plan.

1.I read here that it is recommended as a best practice to set UPN and SMTP to the same address.

2. Also, when you change UPN on prem you need to update it via powershell command (UPN change is not reflected in O365 (happens sometimes)) so that it gets updated on 365 side.
   https://techcommunity.microsoft.com/t5/microsoft-365/rename-users-upn-hybrid-enviornment/m-p/179508
3. When adding a new SSL certificate in your Exchange on-premises deployment, make sure to update all services that use SSL.
4. After running the hybrid configuration wizard, be sure to test that the features of your hybrid deployment are working properly (mail flow, etc.)

Finally, before making any changes, make sure to take a complete backup of Active Directory and Exchange Server. If possible, test it in a test environment first.

This might be helpful:
https://www.alitajran.com/change-users-upn-with-powershell/

(Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)

Regards

SF