Greetings
Having recently discovered Zimbra, we recently showed it to a client who absolutely loves it, but, there is (of course) an issue.
Their current setup is quite complex having had a purpose built plugin written for TBird (see here:
Sendmail/Dovecot to Zimbra Problem for some details) plus a little more processing under the sheets.
1. How difficult would it be for us to provide the same functionality using Zimbra Desktop and ZCS?
2. Can anyone recommend a developer who might be interested in this as a paid project?
Nigel.
Bugzilla
Wiki
Source
Desktop Mods - Where to Start? 
Linear Mode
