javax.mail.MessagingException: Could not connect to SMTP host

如果使用了 SSL 连接请添加配置：spring.mail.properties.mail.smtp.ssl.enable=true

可以参考 /questions/31721298/spring-boot-1-2-5-release-sending-e-mail-via-gmail-smtp

在使用 Spring Boot 发送邮件时遇到了无法连接服务器的问题，使用的是阿里云的邮件服务，配置如下：

spring.mail.host=spring.mail.port=465spring.mail.username=usernamespring.mail.password=passwordspring.mail.properties.smtp.auth=truespring.mail.properties.smtp.starttls.enable=true

MailUtil.java：

import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.mail.MailException;import org.springframework.mail.SimpleMailMessage;import org.springframework.mail.javamail.JavaMailSender;import org.ponent;import org.thymeleaf.TemplateEngine;@Componentpublic class MailUtil {private final Logger logger = LoggerFactory.getLogger(getClass());@AutowiredJavaMailSender mailSender;@AutowiredTemplateEngine templateEngine;public void sendSimpleEmail(String deliver, String[] receiver, String[] carbonCopy, String subject, String content) throws ServiceException {long startTimestamp = System.currentTimeMillis();logger.info("Start send mail ... ");try {SimpleMailMessage message = new SimpleMailMessage();message.setFrom(deliver);message.setTo(receiver);message.setCc(carbonCopy);message.setSubject(subject);message.setText(content);mailSender.send(message);logger.info("Send mail success, cost {} million seconds", System.currentTimeMillis() - startTimestamp);} catch (MailException e) {logger.error("Send mail failed, error message is : {} \n", e.getMessage());e.printStackTrace();throw new ServiceException(e.getMessage());}}}

但是邮件发送一直失败，异常信息如下：

org.springframework.mail.MailSendException: Mail server connection failed; nested exception is javax.mail.MessagingException: Could not connect to SMTP host: , port: 465, response: -1. Failed messages: javax.mail.MessagingException: Could not connect to SMTP host: , port: 465, response: -1; message exception details (1) are:Failed message 1:javax.mail.MessagingException: Could not connect to SMTP host: , port: 465, response: -1at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2106)at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:712)at javax.mail.Service.connect(Service.java:366)at org.springframework.mail.javamail.JavaMailSenderImpl.connectTransport(JavaMailSenderImpl.java:501)at org.springframework.mail.javamail.JavaMailSenderImpl.doSend(JavaMailSenderImpl.java:421)at org.springframework.mail.javamail.JavaMailSenderImpl.send(JavaMailSenderImpl.java:307)at org.springframework.mail.javamail.JavaMailSenderImpl.send(JavaMailSenderImpl.java:296)at .hellowood.mail.util.MailUtil.sendSimpleEmail(MailUtil.java:76)at .hellowood.mail.MailUtilTests.sendSimpleEmail(MailUtilTests.java:48)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)at org.junit.runners.ParentRunner.run(ParentRunner.java:363)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)at org.junit.runners.Suite.runChild(Suite.java:128)at org.junit.runners.Suite.runChild(Suite.java:27)at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)at org.junit.runners.ParentRunner.run(ParentRunner.java:363)at org.junit.runner.JUnitCore.run(JUnitCore.java:137)at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

将端口改为80或25时可以正常发送，没有任何问题，所以问题在于使用465端口时 SSL 的配置出错了，添加了以下配置后问题解决：

spring.mail.properties.mail.smtp.ssl.enable=true