onmicrosoft alias not created for an existing user

Question

One of my users is missing the onmicrosoft.com alias and I cannot add it manually. I have added it to my on prem and it says it synced in AD connect but its not updating the user in Azure users

Answer 1

Have you checked for any potential conflicts/duplicate values? If you are certain the address is not in use, you can use one of the following workarounds:

• Change the user UPN to user@tenant .onmicrosoft.com. As Microsoft enforces a requirement that at least one SMTP address should match the UPN, this will solve the issue. You can change the UPN back to the original value after.
• Use the -WindowsEmailAddress parameter, which allows you to change the primary SMTP address even for synced users. For example: Set-Mailbox user@keyman .com -WindowsEmailAddress user@tenant .onmicrosoft.com

You can change it back to the original value after.

Answer 2

Yes, as michev mentioned if there any conflicts or duplicate value then this is expected behavior so you could use below cmdlet to find if any of users or group has that specific aias. Hope this helps.

User:
get-MsolUser -All | where {$_.userPrincipalName -like "user@tenant.onmicrosoft.com"} 
get-MsolUser -All | where {$_.proxyAddresses -like "user@tenant.onmicrosoft.com"} 
get-MsolUser -All | where {$_.mail -like "user@tenant.onmicrosoft.com"} 
get-MsolUser -All | where {$_.targetAddress -like "user@tenant.onmicrosoft.com"} 

Group: 
get-MsolGroup -All | where {$_.proxyAddresses -like "user@tenant.onmicrosoft.com"} 
get-MsolGroup -All | where {$_.mail -like "user@tenant.onmicrosoft.com"} 
get-MsolGroup -All | where {$_.targetAddress -like "user@tenant.onmicrosoft.com"}