Java.lang.NoClassDefFoundError: javax/mail/MessagingException

Question

This is causing me some headaches in the Sun 8.1 Application Server.
I created an applet which uses the mail api to send error messages to the helpdesk. It works fine when used as an applet outside of the Application Server. But when I configure the applet to work within a JSP and the Sun 8.1 App Server, I get the above error message in my console.
I check to make sure that I had the proper import statement. I checked my spelling. I checked my try clause to make sure I had it properly set-up. I tried running the class using my local mail.jar, and it runs fine. What more can I check?
I need an answer very quickly: as in yesterday.
Dwight

Answer 1

I am compiling using the same jars that are in the
App Server. Compiliation is successful. The problem
arises when I use the JRE. I can run it using the
same JRE outside of the App Server.For some reason, the class is not being loaded into the appserver or by the JSP. Can you reach it from another app in the server? Perhaps you could create a trivial session bean or something to see if the class can be loaded. You know what the problem is so now it's a matter of narrowing down the possible causes.
Classloaders in appservers can be complex. You might want to do some debugging to see what classloader you are using in your JSP and what it's parents are. Can you add the jar to the WAR file?