[Staffslug] Open Source Exchange Alternatives

Hi Friends :) I'm looking for an open source alternative to Zimbra. Up until now I've been using Google Mail/Contacts/Calendar for my personal stuff, but I'm going to be running my own business soon and I'm becoming less and less fond of the idea that my data is not stored locally. The basic features that I'm looking for are: * Email (multiple mailboxes, aliases, groups etc) * Calendar * Accessible by browser * Mobile Sync (Nokia N97) * Easy data portability * Open Source For this reason, I was wondering if anybody on the list had any experience with Zimbra? I would also be grateful for any suggestions besides Zimbra that might suit my needs. Hope everybody has had a good day :) Adam