Rather than bore everyone with the suggestions, I had put it in the bugbase. Feel free to vote:

Bug 27015 – Request a method to add arbitrary LDAP server as shared (Read/Only) addressbook --LDAP suggestion
Bug 38197 – OpenPGP encryption support for ZD --PGP encryption
Bug 38198 – Google Calendar XML and user syncing --Google XML Calendar Sync
Bug 38556 – Ability to import thunderbird's (exported) filters into Zimbra. --Import thunderbird filters
Bug 38644 – Full support for Hotmail POP --Full Hotmail support
Bug 42988 – Calendar Print Views --Calendar Print Views
Bug 42989 – Inner Company IM and Google Talk/ Yahoo Messenger/ ICQ/ AIM etc... --IMing
Bug 42990 – Ability to have all messages in message pain, rather than 50 at a time --Message viewing options.