 +1 on Solaris...
I love Linux all day long. But there are a lot of systems running Solaris (it is after all the most popular UNIX). OpenSolaris/Solaris 10 should be very easy to port to and easy to maintain as well. The Solaris ABI has been consistent for the last decade. Once you release Zimbra for Solaris, you wouldn't have to worry about future versions of Solaris breaking your binary packages -- it's future proof. When you guys release a binary package for a given linux distro you'll have to constantly update the binary package for the newer releases of that distro (and you'll be obliged to maintain and support the old version too). Porting to Solaris would be a one time effort and a feather in Zimbra's "enterprise class" cap.
-Bryan |