I am getting the classnotfoundexception javax/mail/MessagingException using Eclipse/Jetty.
I have added activation.jar, javax.mail-1.5.3.jar, and javaee.jar to my Java build path to my lib folder and war/web-inf/lib folder.
My mistake was that I was trying to execute the code on the client. Once I moved the code to the server it worked great and javaee.jar wasn't required.