I have downloaded Jwebmail source from the above mentioned link. I added it in eclipse as an existing project..and trying to run it as an application.
it gives me following error

java.lang.NoClassDefFoundError: net/wastl/webmail/misc/Helper
Caused by: java.lang.ClassNotFoundException: net.wastl.webmail.misc.Helper
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
Exception in thread "main"

net.wastl.webmail.misc.Helper is already there in the source directory. and that too without any errors.
I don't know why it is giving that error..