I have 20+ email address across 10 domains. I have been using Tbird 7 and it is using lots of resources on my Ubuntu 10.10 desktop. I installed Zimbra Desktop ("ZD") and like it alot. But, some problems exist that are keeping me from transitioning to it:
1. About 1/2 of the email accounts are google mail or google mail via google apps accounts. The others are imap & pop accounts from domains I manage or are yahoo or hotmail accounts.
2. I added 5 email accounts to the ZD that I installed including the google mail account that I use to sync my address book and calendar with Tbird and my Blackberry. I use Google Sync & Google Contacts add-ons in Tbird and Google Sync on the Blackberry.
3. Zimbra doesn't really sync the Calendar - it just imports the items. I cannot change an item in ZD and have it change in Google Calendar. I need this feature to continue using ZD.
4. While Zimbra appears to sync the Google Contacts, it doesn't allow access to them unless an email message is being composed is from that google email address. I need to be able to use the contacts from all email addresses.