Here is the solution given on zimbra bugzilla :
Apparently the solution in Beta3 is a little different.
1)Copy the language files found in the zip file (forgot where I found them, if
someone knows the url please let me know) to the program path of zimbra in the
directory
C:\Program Files\Zimbra\Zimbra Desktop\win32\prism\xulrunner\dictionaries
In my case I copied nl.dic and nl.aff
2)Go on windows XP to the following directory:
C:\Documents and Settings\<username>\Local Settings\Application
Data\Zimbra\Zimbra Desktop\profile
and edit user.
js. Change the line "user_pref("spellchecker.dictionary", "nl")"
into the correct language you need.
3)Stop ZD and make sure that zdesktop.exe is also stopped from the task
manager.
4)Restart ZD. Spell checking should be working now. It is even independent from
your choosen UI language setting. Tested it with nl locale in user.
js and
English UI.
For me it work
