Yes, you can run multiple domain names on your Zimbra server and this does not cost more. Zimbra is licensed on a per mailbox basis. So you can have multiple domains delivering email to the same mailbox and the mailbox can have multiple email addresses which email is sent from. For example: fred@example1.com fred@example2.com fred@example3.com fred@example4.com fred@example5.com sam@example5.com bob@example5.com Can be configured to ALL deliver to Fred's mailbox Fred can then send from any of the fred@example[1 .. 5].com or bob@ or sam@ domains.