This solution applies to the Barracuda Email Security Service.
The Barracuda Email Security Service (BESS) counts the
number of users. If LDAP is set up correctly, then BESS will determine aliases, and they will not be counted towards the number of users.
Also, multiple domains can be set up as domain-level aliases of each other to prevent double counting of users. If LDAP is not used, users will need to be entered manually to setup any aliases with the Linked Account feature in User > Settings.
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