Hi monvural,
Thanx for you hint, it bring me in the right direction
Just in case it would be useful to someone, I had to add /opt/zimbra/lib/jars/zimbracommon.jar to the classpath in my tomcat startup script to make it working.
The weird thing is that the zimbra tomcat startup script and tomcat's error message let you suppose it has to be present in java.library.path, not in classpath. Maybe some platform specific issue here ?
Julien