Exchange AD Objects with an Incorrect Target Address Attribute

Within an Hybrid environment , you can notice that a new accepted domain is in the Exchange portal

Mail.onmicrosoft.com

This domain is going to be used by the on premises to route mail of the account that has been migrated

A quick way to view an objects Active Directory targetAddress attribute is through the Active Directory Users and Computers panel. In AD Users and Computers, ensure that Advanced Features has been enabled under the View menu.

The following PowerShell can be run against on-premises Active Directory and will display any AD user that does not have a targetAddress that ends in mail.onmicrosoft.com.

Get-aduser -filter {targetAddress -notlike “*.mail.onmicrosoft.com”} -properties * | Select-Object Name,targetAddress

All the accounts not matching this could have issues . So make sure all your accounts have target address corrected in your Hybrid environment.