The process

  1. Connect to EXOL online (Read this post for more infomation) Connecting to Services.
  2. Run the below command to add the required SMTP address as an alias. $UPN is the current Primary Email address and $newUPN is what you would like to change it too. Example below
$UPN="[email protected]"
$NewUPN="[email protected]"

Set-UnifiedGroup -Identity "$UPN" -EmailAddresses: @{Add ="$NewUPN"}
  1. Promote alias as a primary SMTP address, Set-UnifiedGroup -Identity $UPN -PrimarySmtpAddress $NewUPN
  2. If not required, you can remove first ID using below command. Set-UnifiedGroup -Identity $NewUPN -EmailAddresses: @{Remove=$UPN}

Please note, For updating the Office 365 group SMTP address required Global Administrator access.

Bonus

I was doing this to migrate an O365 group to a Shared Mailbox, the below you can use to add the UPN to a shared Mailbox.

$SharedUPN = "[email protected]"
Set-Mailbox $sharedUPN -EmailAddresses @{Add=$UPN}

This post is a “just for documentation (JFD)” post which I use for my reference, but I have made public as it may be useful. I put less time into these posts as they are my reference. If you would like more information or some help post a comment, and I can see what I can do.