无法发送邮件 - javax.net.ssl.SSLException：无法识别的 SSL 消息，纯文本连接？

Question

We are sending Mail using Spring JavaMailSenderImpl . Following is the configuration

 <bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">
        <property name="host" value="${host}"/>
        <property name="port" value="${port}"/>
        <property name="username" value="${mail.username}"/>
        <property name="password" value="${mail.password}"/>
        <property name="javaMailProperties">
            <props>
                <!-- Use SMTP transport protocol -->
                <prop key="mail.transport.protocol" >${mail.transport.protocol}</prop>
                <!-- Use SMTP-AUTH to authenticate to SMTP server -->
                <prop key="mail.smtp.auth">${mail.smtp.auth}</prop>
                <!-- Use TLS to encrypt communication with SMTP server -->
                <prop key="mail.smtp.starttls.enable">${mail.smtp.starttls.enable}</prop>
                <prop key="mail.debug">false</prop>
                <prop key="mail.smtp.ssl.enable">true</prop>
            </props>
        </property>
    </bean>

Properties File :-

host=XXXX.XXXX.XX
port=25
mail.username=xxxxxxxx
mail.password=xxxxxxx
mail.transport.protocol=smtp
mail.smtp.auth=true
mail.smtp.starttls.enable=true

Console Logs

Exception in thread "taskExecutor-2" org.springframework.mail.MailSendException: Mail server connection failed; nested exception is javax.mail.MessagingException: Could not connect to SMTP host: XXXX.XXXX.XX, port: 25;
      nested exception is:
            javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?. Failed messages: javax.mail.MessagingException: Could not connect to SMTP host: XXXX.XXXX.XX, port: 25;
      nested exception is:
            javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?; message exception details (1) are:
    Failed message 1:
    javax.mail.MessagingException: Could not connect to SMTP host: XXXX.XXXX.XX, port: 25;
      nested exception is:
            javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
            at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1934)
            at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:638)
            at javax.mail.Service.connect(Service.java:295)
            at org.springframework.mail.javamail.JavaMailSenderImpl.doSend(JavaMailSenderImpl.java:389)
            at org.springframework.mail.javamail.JavaMailSenderImpl.send(JavaMailSenderImpl.java:340)
            at org.springframework.mail.javamail.JavaMailSenderImpl.send(JavaMailSenderImpl.java:336)
            at com.XXXX.Mailer$1.run(Mailer.java:52)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
            at java.lang.Thread.run(Thread.java:744)
    Caused by: javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
            at sun.security.ssl.InputRecord.handleUnknownRecord(InputRecord.java:671)
            at sun.security.ssl.InputRecord.read(InputRecord.java:504)
            at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:927)
            at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1312)
            at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1339)
            at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1323)
            at com.sun.mail.util.SocketFetcher.configureSSLSocket(SocketFetcher.java:507)
            at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:238)
            at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1900)
            ... 9 more

We are convinced that this is not related to the SSL certificate as there are other web applications deployed in the same server which sends email perfectly with the same configuration. What could be the issue here ?

Answer 1

<prop key="mail.smtp.starttls.enable">${mail.smtp.starttls.enable}</prop>
<prop key="mail.smtp.ssl.enable">true</prop>

You want either mail.smtp.ssl.enable for implicit SSL directly after TCP connect (port 465) or mail.smtp.starttls.enable for explicit SSL using the STARTTLS command (port 25). But with your current properties you set both to true.

This means it will do a TCP connect to port 25 and try a SSL handshake there. This will fail because the server is sending a plain text greeting from the SMTP dialog and not the expected SSL handshake. Thus you get

Unrecognized SSL message, plaintext connection?

To fix it make sure that you either use implicit or explicit SSL but not both depending on the port, ie for port 25 mail.smtp.ssl.enable should be false.

Answer 2

I tried to resolve this by many methods but finally found this working by myself.

1. Make sure you are able to send emails from Terminal or by any other mail client before creating code. Once your have tested mail is working fine then use below properties and code. I have deployed the Code in the Email server so I don't require SSL or TLS. I am using port 25 for Relay.

2. Required Properties -

    mail.smtp.host=<myhostname.com> mail.smtp.port=25 mail.smtp.auth=true mail.transport.protocol=smtp smtpd_recipient_restrictions=permit_sasl_authenticated user=<sender_username/email> password=<password> mail.smtp.username=<sender_username/email> mail.smtp.password=<password>

3. Required Code -

    public String sendEmail(String email){ //Compose the message try { FileReader reader=new FileReader("smtp.properties"); //Get the session object Properties props = new Properties(); props.load(reader); System.out.println(" Props :: " + props.toString()); String to = email; String host=props.getProperty("mail.smtp.host"); final String user=props.getProperty("user"); final String password=props.getProperty("password"); Session session = Session.getInstance(props, new javax.mail.Authenticator() { protected PasswordAuthentication getPasswordAuthentication() { return new PasswordAuthentication(user, password); } }); Message message = new MimeMessage(session); message.setFrom(new InternetAddress(user)); message.setRecipients( Message.RecipientType.TO, InternetAddress.parse(to) ); message.setSubject("Testing - SMTP"); message.setText("Dear User, \\n\\n Hello !"); Transport.send(message); System.out.println("Done"); } catch (MessagingException e) { e.printStackTrace(); } catch (IOException ex) { ex.printStackTrace(); } return "SUCCESS"; }

4. Required Imports -

    import javax.mail.*; import javax.mail.internet.InternetAddress; import javax.mail.internet.MimeMessage; import java.util.Properties;

Answer 3

问题出现在 javax.mail 1.4.0 中，升级到 1.4.7 解决了我的问题