Answer by della raharjo for Sending Email in Android using JavaMail API without using the default/built-in app

To add attachment, don't forget to add.

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");    CommandMap.setDefaultCommandMap(mc);