✨(aliases) import existing aliases from dimail

import existing aliases from dimail, making sure usernames don't clash with
existing mailboxes. Convenient when people fall out of sync
with dimail or for domains partially operated outside people.

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to
 
 ## [Unreleased]
 
+- ✨(aliases) import existing aliases from dimail
 - 🛂(permissions) return 404 to users with no access to domain #985 
 - ✨(aliases) can create, list and delete aliases #974