无法连接到SMTP主机：SMTP.gmail.com，端口：587；嵌套异常为：java.net.ConnectException：连接超时：connect

Question

下面是应用程序的代码。我一直在尝试使用eclipse IDE来运行它。我还添加了所有必需的java邮件jar文件，即dsn.jar、imap.jar、mailapi.jar、pop3.jar、smtp.jar、mail.jar。但会出现以下错误无法连接到SMTP主机：SMTP.gmail.com,port:587。

没有防火墙阻止访问，因为ping smtp.gmail.com时会收到回复。我甚至这样试过：

null

    package net.codejava.mail;

    import java.util.Date;
    import java.util.Properties;

    import javax.mail.Authenticator;
    import javax.mail.Message;
    import javax.mail.MessagingException;
    import javax.mail.PasswordAuthentication;
    import javax.mail.Session;
    import javax.mail.Transport;
    import javax.mail.internet.AddressException;
    import javax.mail.internet.InternetAddress;
    import javax.mail.internet.MimeMessage;

    public class PlainTextEmailSender {

        public void sendPlainTextEmail(String host, String port,
                final String userName, final String password, String toAddress,
                String subject, String message) throws AddressException,
                MessagingException {

            // sets SMTP server properties
            Properties properties = new Properties();
            properties.put("mail.smtp.host", host);
            properties.put("mail.smtp.port", port);
            properties.put("mail.smtp.auth", "true");
            properties.put("mail.smtp.starttls.enable", "true");

            // creates a new session with an authenticator
            Authenticator auth = new Authenticator() {
                public PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(userName, password);
                }
            };

            Session session = Session.getInstance(properties, auth);

            // creates a new e-mail message
            Message msg = new MimeMessage(session);

            msg.setFrom(new InternetAddress(userName));
            InternetAddress[] toAddresses = { new InternetAddress(toAddress) };
            msg.setRecipients(Message.RecipientType.TO, toAddresses);
            msg.setSubject(subject);
            msg.setSentDate(new Date());
            // set plain text message
            msg.setText(message);

            // sends the e-mail
            Transport.send(msg);

        }

        /**
         * Test the send e-mail method
         *
         */
        public static void main(String[] args) {
            // SMTP server information
            String host = "smtp.gmail.com";
            String port = "587";
            String mailFrom = "user_name";
            String password = "password";

            // outgoing message information
            String mailTo = "email_address";
            String subject = "Hello my friend";
            String message = "Hi guy, Hope you are doing well. Duke.";

            PlainTextEmailSender mailer = new PlainTextEmailSender();

            try {
                mailer.sendPlainTextEmail(host, port, mailFrom, password, mailTo,
                        subject, message);
                System.out.println("Email sent.");
            } catch (Exception ex) {
                System.out.println("Failed to sent email.");
                ex.printStackTrace();
            }
        }
    }

Answer 1

就像我说的，你的代码没有问题。如果有的话，只是为了做一些测试，试着删除身份验证部分，看看它是否起作用：

    public void sendPlainTextEmail(String host, String port,
            final String userName, final String password, String toAddress,
            String subject, String message) throws AddressException,
            MessagingException {

        // sets SMTP server properties
        Properties properties = new Properties();
        properties.put("mail.smtp.host", host);
        properties.put("mail.smtp.port", port);
        properties.put("mail.smtp.auth", "true");
        properties.put("mail.smtp.starttls.enable", "true");
// *** BEGIN CHANGE
        properties.put("mail.smtp.user", userName);

        // creates a new session, no Authenticator (will connect() later)
        Session session = Session.getDefaultInstance(properties);
// *** END CHANGE

        // creates a new e-mail message
        Message msg = new MimeMessage(session);

        msg.setFrom(new InternetAddress(userName));
        InternetAddress[] toAddresses = { new InternetAddress(toAddress) };
        msg.setRecipients(Message.RecipientType.TO, toAddresses);
        msg.setSubject(subject);
        msg.setSentDate(new Date());
        // set plain text message
        msg.setText(message);

// *** BEGIN CHANGE
        // sends the e-mail
        Transport t = session.getTransport("smtp");
        t.connect(userName, password);
        t.sendMessage(msg, msg.getAllRecipients());
        t.close();
// *** END CHANGE

    }

这就是我每天使用的从应用程序中发送几十封电子邮件的代码，并且100%保证可以工作--当然，只要smtp.gmail.com:587是可访问的。