Easy question but long solution... One way is to navigate to Exch Admin, Config, Site Addressing, Site Addressing tab. If you click the Help button it will show you how to change the default addresses when created. After you make the change it will prompt you to change all existing addresses to the new format. Be careful though, some things may get changed you didn't necessarily want changed. Anothe way is... ...to run a directory export of all mailboxes. After opening the CSV file created, I would create a macro (Q113237) to create new SMTP addresses. I would test it by copying only one of the entries in the CSV file to a new file, running the newly created macro against that one entry. If you get the desired results, run it against the original CSV file. Then import the file to make all of the changes.