What's the mean of the error message?

I have done a simple code to send an emailfro the command line, i've done the same using servlet and it was successful, so now when i run a class to send an email i get this message, what's wrong ? i have set the debug.The lines of the EnviaEmail.java:36 is

35session.setDebug(true);

36Message msg =new MimeMessage(session);

and the lines of Teste.main(Teste.java:27) is

27exe.send(smtpHost,smtpPort, smtpUser, smtpPass, end, para, assunto, conteudo,null);

DEBUG: setDebug: JavaMail version 1.3.2

Exception in thread "main" java.lang.NoClassDefFoundError: com/sun/mail/util/SharedByteArrayInputStream

at send_email.EnviaEmail.send(EnviaEmail.java:36)

at send_email.Teste.main(Teste.java:27)

Java Result: 1

BUILD SUCCESSFUL (total time: 20 seconds)

thanks!!

[935 byte] By [Sonecaa] at [2007-10-2 15:57:00]