Great news BUT there is total showstopper still: NO PGP/GPG SUPPORT.
How this can be true in 2010? It's mandatory to have strong open source encryption available and supported in any e-mail client. GnuPG is one of those absolute mandatory encryption engines that ZD must support. S-MIME after that.
I really waited fot ZD2 but this is totally useless without GPG encryption support. Over 60% of my emails are encrypted by default, even those the topic it selves is puplic and general chat. It's just an princible to do so. This is trivial peace of work to do by your resources and as this is open source, you should implement code from all ready done plugins like Enigmail plugin for Thunderbird.
Now - can't use it - no sense to recomend to anyone. Other wise it looks solid and robust client ...BUT!
This is something witch must be implemented on client side first, after that you should think big and hit on enterprise level issues on GPG/PGP encryption and do it in your server side. Privacy and security is no#1 issue in e-mails. Ignoring GPG/PGP is just amaging... Where's the beef here?
Thanks anyway for this free software. There must be a lot of users witch are totally happy with this. I hope that someday you are also interested in privacy and security issues. I lay back and wait for ZD3.