I'm currently running my mail server on a Dell 1U rack server. I have Postfix for smtp, Dovecot for imaps and squirrelmail for http and https. Mail is stored in maildir format and credentials are garnered from windows active directory. Works great but no collaboration. I am reading up on zimbra so I can plan a migration. Has anyone ever migrated from a setup similar to mine to Zimbra? Any advice would be appreciated.