Find all empty Google groups (without any members internal or external ) and their aliases in order to show when they were last used
It will display primary group email and its aliases showing when it was last used
To do this, open GAT+ and navigate to Groups audit.
Select Last used address and apply a custom filter
Under Type select Empty groups last used address
Click on Apply
Optionally you will see in what area ( drive, email, calendar ) the group primary email and its aliases last used.
The selected address (alias) is not used so it can be removed.