In Mail class,

Session session = Session.getDefaultInstance(mailServerProperties, null);

If the mail server requires user authentication, this condition is not handled in mail class. So I created one custom class which extends Mail class.

 if(auth) {
 session = Session.getDefaultInstance(mailServerProperties, new Authenticator() {
 public PasswordAuthentication getPasswordAuthentication() {
 return new PasswordAuthentication(userName, password);
 }
 });
 } else {
 session = Session.getDefaultInstance(mailServerProperties, null);
 }
this is not complete code...
made changes in jbpm.cf.xml file
<string name='jbpm.mail.class.name' value='org.jbpm.mail.CustomMail'/>
and put this custommail class file in web inf folder of jbpm-console war file...
But when i used mail-node in process definition, still it delegates request to old Mail class not the CustomMail class.