Unable to send an email using SMTP (Getting javax.

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 = "[e-mail]";
        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("[e-mail]"));
            message.setRecipients(Message.RecipientType.TO,
            InternetAddress.parse("[e-mail]"));
            message.setSubject("Testing Subject");
            message.setText("Dear Mail Crawler,"
                + "\n\n 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 had this problem. the reason was our administrator had blocked TLS and SSL protocols.

Answer 2

It looks like the SSL implementation used by your server is not compatible with the SSL implementation in the version of the JDK you're using. The file SSLNOTES.txt (also included in the JavaMail download bundle) has some debugging tips. You might need a JDK SSL expert to sort this out.

Answer 3

If you don't want to use SSL, and you're using smtp instead of smtps try these settings

mail.smtp.starttls.enable=false
mail.transport.protocol=smtp