I migrated a mid-size company from Exchange server to Zimbra Open Source edition and it seems it quite faster and much better handles mailboxes over 2 GB in size (actually, some of users have mailboxes over 10 GB in size, architects, lots of pictures)

But I have problems with most of users when sending mail inside their domain. Outlook remembered previous e-mail addesses as:

John Smith <john.smith>

and it worked inside Exchange since that was their username.

But in Zimbra it does not.
Since there are over 50 users, it would be pain in the ass to walk around all users and remove wrong AutoSuggest entries for each of them.

What I need to do on Zimbra server to enable aliases without @domain.com part?