Q: Why email notification is not sent, and what are these JavaMail Exceptions?
   (SecurityException, NoSuchProviderException, NoClassDefFoundError)

A: Email notification is not sent because of these exceptions:
   javax.mail.NoSuchProviderException: smtp
   or
   javax.activation.UnsupportedDataTypeException: no object DCH for MIME type text/plain

   These error messages are produced by JavaMail and are completely misleading. 
   The root cause of the error is a mis-matched or a duplicate pair of mail.jar and
   activation.jar. Bugzero packaged mail.jar and activation.jar under WEB-INF/lib,
   and if your servlet engine have its own pair of jars in its common or shared lib,
   problem may arise. A simple solution is to remove one pair of mail.jar and
   activation.jar either from Bugzero's WEB-INF/lib directory, or from servlet engine's
   common/share lib directory. 

   You may also see 
     java.lang.SecurityException: Access to default session denied
   and/or subsequent
     java.lang.NoClassDefFoundError
   The cause of the error is the same as above, and so removing one pair of mail.jar
   and actovation.jar shall solve the problem. Note that, you should not just rename
   the files, you should either remove them completely or move them out of the way so
   that the application server cannot find them.