java - Unable to send an email using SMTP (Getting javax.mail.MessagingException: Could not convert socket to TLS;)

Question

I have written the following code for sending email using javamail API through SMTP as TLS as SSL is not supported but I ended up with the following exception. Please see my code below. I have used debugging mode and below the code you can find the exception as well.

import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class SendMailTLS {

    public static void main(String[] args) {

        final String username = "[email protected]";
        final String password = "***********";

        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", "mail.mydomain.com");
        props.put("mail.smtp.debug", "true");
        props.put("mail.smtp.port", "587");

        Session session = Session.getInstance(props,
          new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(username, password);
            }
          });
        session.setDebug(true);

        try {

            Message message = new MimeMessage(session);
            message.setFrom(new 
                  InternetAddress("[email protected]"));
            message.setRecipients(Message.RecipientType.TO,
            InternetAddress.parse("[email protected]"));
            message.setSubject("Testing Subject");
            message.setText("Dear Mail Crawler,"
                + "

 No spam to my email, please!");

            Transport.send(message);

            System.out.println("Done");

        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
    }
}

Exception trace

DEBUG: setDebug: JavaMail version 1.4.5
DEBUG: getProvider() returning javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Sun Microsystems, Inc]
DEBUG SMTP: useEhlo true, useAuth true
DEBUG SMTP: useEhlo true, useAuth true
DEBUG SMTP: trying to connect to host "mail.mydomain.com", port 587, isSSL false
220-cpanel35.per.syra.net.au ESMTP Exim 4.80 #2 Fri, 05 Oct 2012 17:28:56 +0800 
220-We do not authorize the use of this system to transport unsolicited, 
220 and/or bulk e-mail.
DEBUG SMTP: connected to host "mail.mydomain.com", port: 587

EHLO xxxxxx.xxxxx.com
250-cpanel35.per.syra.net.au Hello xxxx.xxxxx.com [xx.xx.xx.xxx]i
250-SIZE 52428800
250-8BITMIME
250-PIPELINING
250-AUTH PLAIN LOGIN
250-STARTTLS
250 HELP
DEBUG SMTP: Found extension "SIZE", arg "52428800"
DEBUG SMTP: Found extension "8BITMIME", arg ""
DEBUG SMTP: Found extension "PIPELINING", arg ""
DEBUG SMTP: Found extension "AUTH", arg "PLAIN LOGIN"
DEBUG SMTP: Found extension "STARTTLS", arg ""
DEBUG SMTP: Found extension "HELP", arg ""
STARTTLS
220 TLS go ahead
Exception in thread "main" java.lang.RuntimeException: javax.mail.MessagingException: Could not convert socket to TLS;
  nested exception is:
    javax.net.ssl.SSLException: java.lang.RuntimeException: Could not generate DH keypair
    at SendMailTLS.main(SendMailTLS.java:52)
Caused by: javax.mail.MessagingException: Could not convert socket to TLS;
  nested exception is:
    javax.net.ssl.SSLException: java.lang.RuntimeException: Could not generate DH keypair
    at com.sun.mail.smtp.SMTPTransport.startTLS(SMTPTransport.java:1918)
    at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:652)
    at javax.mail.Service.connect(Service.java:317)
    at javax.mail.Service.connect(Service.java:176)
    at javax.mail.Service.connect(Service.java:125)
    at javax.mail.Transport.send0(Transport.java:194)
    at javax.mail.Transport.send(Transport.java:124)
    at SendMailTLS.main(SendMailTLS.java:47)
Caused by: javax.net.ssl.SSLException: java.lang.RuntimeException: Could not generate DH keypair
    at sun.security.ssl.Alerts.getSSLException(Alerts.java:208)
    at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1868)
    at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1826)
    at sun.security.ssl.SSLSocketImpl.handleException(SSLSocketImpl.java:1809)
    at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1328)
    at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1305)
    at com.sun.mail.util.SocketFetcher.configureSSLSocket(SocketFetcher.java:548)
    at com.sun.mail.util.SocketFetcher.startTLS(SocketFetcher.java:485)
    at com.sun.mail.smtp.SMTPTransport.startTLS(SMTPTransport.java:1913)
    ... 7 more
Caused by: java.lang.RuntimeException: Could not generate DH keypair
    at sun.security.ssl.DHCrypt.<init>(DHCrypt.java:123)
    at sun.security.ssl.ClientHandshaker.serverKeyExchange(ClientHandshaker.java:618)
    at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:202)
    at sun.security.ssl.Handshaker.processLoop(Handshaker.java:868)
    at sun.security.ssl.Handshaker.process_record(Handshaker.java:804)
    at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:998)
    at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1294)
    at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1321)
    ... 11 more
Caused by: java.security.InvalidAlgorithmParameterException: Prime size must be multiple of 64, and can only range from 512 to 1024 (inclusive)
    at com.sun.crypto.provider.DHKeyPairGenerator.initialize(DHKeyPairGenerator.java:120)
    at java.security.KeyPairGenerator$Delegate.initialize(KeyPairGenerator.java:658)
    at sun.security.ssl.DHCrypt.<init>(DHCrypt.java:117)
    ... 18 more

Can anyone help me debug this? Thanks in advance!

Answer 1

I resolved this issue by just commenting out the below property

props.put("mail.smtp.starttls.enable", "true"); 

and the code got executed with no errors or warning or simply delete this line from the above source code. It is working like a charm till date.