解决问题：javax.mail.MessagingException: Could not connect to SMTP host: smtp.exmail.qq.com port: 25;

最近项目中需要用到发送邮件这一功能，总是遇到这样的一个报错：

javax.mail.MessagingException: Could not connect to SMTP host: smtp., port: 25;

nested exception is:

.ConnectException: Connection timed out: connect

at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1961)

at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:654)

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:253)

at javax.mail.Transport.send(Transport.java:124)

at io.batcloud.util.SendMail.send(SendMail.java:150)

at io.batcloud.util.MessageSentTool.sent(MessageSentTool.java:80)

at io.batcloud.task.SentEmailByThread.dotask(SentEmailByThread.java:59)

at io.batcloud.task.SentEmailByThread.run(SentEmailByThread.java:36)

at java.lang.Thread.run(Thread.java:745)

Caused by: .ConnectException: Connection timed out: connect

at .DualStackPlainSocketImpl.connect0(Native Method)

at .DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)

at .AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)

at .AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)

at .AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)

at .PlainSocketImpl.connect(PlainSocketImpl.java:172)

at .SocksSocketImpl.connect(SocksSocketImpl.java:392)

at .Socket.connect(Socket.java:579)

at .Socket.connect(Socket.java:528)

at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:299)

at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:234)

at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1927)

... 11 more

因为需要发送多个邮箱，比如一个邮件任务里，需要发送把同一个内容发送到几十个或者更多的邮件，为了做到群发单显，所以不能一次性把所有人都写在收件人那里，这样会暴露其他收件的邮箱地址，于是只能一个循环地发送。但是发了第一第二个之后，从第三个开始，总是会有这样的报错发生。

奉劝各位一句，不要用Transport.send(message);这个静态方法来发送邮件。因为这个方法会连接服务器，然后发送邮件，然后关闭邮件服务器，如果发送的邮件多了，就会重复同样的动作，导致报以上的错误。这样可能会邮件服务器那边拒绝掉。尤其是公共的那些邮件服务器。

后来，我改用我在发送的时候使用

transport = session.getTransport();

transport.connect();

然后发送邮件

transport.sendMessage(message, message.getAllRecipients());

等判断所有邮件都发送完毕了，再

transport.close();

这样就可以顺利发送多个邮件了。