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

Question

我们使用 Spring JavaMailSenderImpl 发送邮件。下面是配置

 <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>

属性文件：-

 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

控制台日志

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

我们确信这与 SSL 证书无关，因为在同一台服务器上部署了其他 Web 应用程序，它们使用相同的配置完美地发送电子邮件。这里可能是什么问题？

原文由 ArunM 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

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

您想要 mail.smtp.ssl.enable 在 TCP 连接（端口 465）之后直接用于隐式 SSL，或者 mail.smtp.starttls.enable 用于使用 STARTTLS 命令（端口 25）的显式 SSL。但是使用您当前的属性，您将两者都设置为 true。

这意味着它将执行 TCP 连接到端口 25 并尝试在那里进行 SSL 握手。这将失败，因为服务器正在从 SMTP 对话框发送纯文本问候语，而不是预期的 SSL 握手。这样你就得到

无法识别的 SSL 消息，明文连接？

要修复它，请确保您使用隐式或显式 SSL，但不能同时使用这两种 SSL，具体取决于端口，即对于端口 25 mail.smtp.ssl.enable 应该是 false。

原文由 Steffen Ullrich 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

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

原文由 Piotr 发布，翻译遵循 CC BY-SA 4.0 许可协议