To help customers with these types of failures, we created a PowerShell-based tool, DLT365Groupsupgrade, that checks the DL being upgraded for any blockers that might cause upgrade failure.
Using the DL Upgrade Troubleshooter
In this example, we’re upgrading a DL called DemoDL; however, it won’t upgrade, and no error is reported:
Running the tool on DemoDL shows a blocker that causes the upgrade process to fail:
The blocker is an existing email address policy (EAP). The DL’s PrimarySmtpAddress is “@Hazem.exohybridlabs.com” but the EnabledPrimarySMTPAddressTemplate on the EAP is “@hazem.exohybridlabs.com.” This indicates that the EAP comparison condition is case-sensitive.
There are 2 ways to remove this blocker. You can recreate the DL with the correct primary smtp address, or you can use the following steps to remove the SMTP alias containing “@Hazem.exohybridlabs.com.”