javax.activation.UnsupportedDataTypeException: no object DCH for MIME type multipart/mixed; boundary

JavaMail depends on some configuration files to map MIME types to Java classes (e.g., multipart/mixed to javax.mail.internet.MimeMultipart). These configuration files are loaded using the ClassLoader for the application. If the ClassLoader doesn't function properly, these configuration files won't be found.

You can simply add below lines .. that solves the issue .

MailcapCommandMap mc = (MailcapCommandMap) CommandMap.getDefaultCommandMap(); 
mc.addMailcap("text/html;; x-java-content-handler=com.sun.mail.handlers.text_html"); 
mc.addMailcap("text/xml;; x-java-content-handler=com.sun.mail.handlers.text_xml"); 
mc.addMailcap("text/plain;; x-java-content-handler=com.sun.mail.handlers.text_plain"); 
mc.addMailcap("multipart/*;; x-java-content-handler=com.sun.mail.handlers.multipart_mixed"); 
mc.addMailcap("message/rfc822;; x-java-content- handler=com.sun.mail.handlers.message_rfc822"); 

This issue can get a solution by taking up the below two steps.

1. Make sure java mail is 1.4.7.(Previously I used 1.4.5 which led to all confusions). Download it from http://www.oracle.com/technetwork/java/index-138643.html
2. Add this piece of code before sending the message:

    Thread.currentThread().setContextClassLoader( getClass().getClassLoader() );

Adding the current thread before sending the email is the solution:

Thread.currentThread().setContextClassLoader( getClass().getClassLoader() );