An Account Alias is an alternative name assigned to a CommuniGate Pro Account. Each Account can have zero, one, or several Account Aliases.
For example, the Account j.smith in the domain2.com Domain can have aliases smith and jsmith. Mail sent to the email@example.com address will be stored in the j.smith Account, and attempts to login as firstname.lastname@example.org will open the same j.smith Account.
You can use Forwarders to assign alternative name for Accounts, too. If you create the Forwarder js in the domain2.com Domain, and make it point to the j.smith address, it will work as yet another alias for the j.smith Account.
If you rename the Account j.smith into james.smith, all Account Aliases will "move" with it - smith and jsmith will remain the Aliases for the james.smith Account. If you remove the Account, the Account Aliases will be removed, too.
Renaming and removing of Accounts has no effect on the Forwarders: if you rename or remove the j.smith Account, the Forwarder js will continue to point to the j.smith address.
As a result, it is not recommended to use Forwarders where you can use Aliases. Forwarders should be used to create "objects" that redirect mail to other Domains or to other mail servers.