Ivoks, Zimbra has major problems. The first issue is that they have an evil license. And then you get to what they bundle with Zimbra, in hacked versions of Postfix, MySQL, apache, Cyrus and more. You can see it all in the ThirdParty section of their svn. A beautiful security nightmare, if you ask me.
Then there is their Evolution conector:
Zimbra is hardcoded against Evolution 2.6/2.8, and not 2.12see this mail posted to the evolution-hackers list.
All of this points to an "all mine, none for you" development ethos. When I asked a Zimbra rep at either Ubuntu Live or OSCON 2007 about their massive patches, the only response was "they didn't do what we wanted and the patches are not suitable to go upstream".
And yes, Ubuntu is far more than Canonical. I was specifically referring to where Canonical should spend it's money in the next year. It should also be noted that in most cases Canonical use cases align very nicely with community ones.
As for Evolution, I widely suspect the only bit we will still be talking about in 5 years will be Evolution-Data-Server (or a succesor).