通过 SMTP 发送电子邮件时出错

Question

我正在尝试使用 gmail 作为 SMTP 通过 Java 代码发送电子邮件。但得到如下异常。你能告诉我为什么找不到gmail主机吗？我在办公网络中工作，不确定是否有防火墙阻止它发送。如果有，出路是什么？

Exception in thread "main" com.sun.mail.util.MailConnectException: Couldn't connect to host, port: smtp.gmail.com, 586; timeout -1;
  nested exception is:
    java.net.UnknownHostException: smtp.gmail.com
    at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2053)
    at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:697)
    at javax.mail.Service.connect(Service.java:364)
    at javax.mail.Service.connect(Service.java:245)
    at mail.JavaEmail.sendEmail(JavaEmail.java:72)
    at mail.JavaEmail.main(JavaEmail.java:22)
Caused by: java.net.UnknownHostException: smtp.gmail.com

Java 源代码：

package mail;

import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
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 JavaEmail
{
    Session mailSession;

    public static void main(String args[]) throws AddressException,    MessagingException
    {
        JavaEmail javaEmail = new JavaEmail();
        javaEmail.setMailServerProperties();
        javaEmail.draftEmailMessage();
        javaEmail.sendEmail();
    }

    private void setMailServerProperties()
    {
        Properties emailProperties = System.getProperties();
        emailProperties.put("mail.smtp.port", "586");
        emailProperties.put("mail.smtp.auth", "true");
        emailProperties.put("mail.smtp.starttls.enable", "true");
        mailSession = Session.getDefaultInstance(emailProperties, null);
    }

    private MimeMessage draftEmailMessage() throws AddressException, MessagingException
    {
        String[] toEmails = { "to-mail@gmail.com" };
        String emailSubject = "Test email subject";
        String emailBody = "This is an email sent by JAVA Code";
        MimeMessage emailMessage = new MimeMessage(mailSession);
        /**
         * Set the mail recipients
         * */
        for (int i = 0; i < toEmails.length; i++)
        {
            emailMessage.addRecipient(Message.RecipientType.TO, new InternetAddress(toEmails[i]));
        }
        emailMessage.setSubject(emailSubject);
        /**
         * If sending HTML mail
         * */
        emailMessage.setContent(emailBody, "text/html");
        /**
         * If sending only text mail
         * */
        //emailMessage.setText(emailBody);// for a text email
        return emailMessage;
    }

    private void sendEmail() throws AddressException, MessagingException
    {
        /**
         * Sender's credentials
         * */
    String fromUser = "from-user@gmail.com";
        String fromUserEmailPassword = "*****";

        String emailHost = "smtp.gmail.com";
        Transport transport = mailSession.getTransport("smtp");
        transport.connect(emailHost, fromUser, fromUserEmailPassword);
        /**
         * Draft the message
         * */
        MimeMessage emailMessage = draftEmailMessage();
        /**
         * Send the mail
         * */
        transport.sendMessage(emailMessage, emailMessage.getAllRecipients());
        transport.close();
        System.out.println("Email sent successfully.");
    }
}

Answer 1

您连接到错误的端口。 Google 的 TLS SMTP 服务器是 587。您可以在此处查看更多信息：http://email.about.com/od/accessinggmail/f/Gmail_SMTP_Settings.htm

Answer 2

这可能对你有帮助

Properties props = new Properties();   
        props.setProperty("mail.transport.protocol", "smtp");   
        props.setProperty("mail.host", mailhost);   
        props.put("mail.smtp.auth", "true");   
        props.put("mail.smtp.port", "465");   
        props.put("mail.smtp.socketFactory.port", "465");   
        props.put("mail.smtp.socketFactory.class",   
                "javax.net.ssl.SSLSocketFactory");   
        props.put("mail.smtp.socketFactory.fallback", "false");   
        props.setProperty("mail.smtp.quitwait", "false");   

        session = Session.getDefaultInstance(props, this);

Answer 3

以下代码可以帮助您解决问题，它的工作......

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;

public class Email {

private static String USER_NAME = "username";  // GMail user name (just the part before "@gmail.com")
private static String PASSWORD = "password"; // GMail password

private static String RECIPIENT = "xxxxx@gmail.com";

public static void main(String[] args) {
String from = USER_NAME;
String pass = PASSWORD;
String[] to = { RECIPIENT }; // list of recipient email addresses
String subject = "Java send mail example";
String body = "hi ....,!";

sendFromGMail(from, pass, to, subject, body);
}

private static void sendFromGMail(String from, String pass, String[] to, String subject, String body) {
Properties props = System.getProperties();
String host = "smtp.gmail.com";

props.put("mail.smtp.starttls.enable", "true");

props.put("mail.smtp.ssl.trust", host);
props.put("mail.smtp.user", from);
props.put("mail.smtp.password", pass);
props.put("mail.smtp.port", "587");
props.put("mail.smtp.auth", "true");


Session session = Session.getDefaultInstance(props);
MimeMessage message = new MimeMessage(session);

try {


    message.setFrom(new InternetAddress(from));
    InternetAddress[] toAddress = new InternetAddress[to.length];

    // To get the array of addresses
    for( int i = 0; i < to.length; i++ ) {
        toAddress[i] = new InternetAddress(to[i]);
    }

    for( int i = 0; i < toAddress.length; i++) {
        message.addRecipient(Message.RecipientType.TO, toAddress[i]);
    }



    message.setSubject(subject);
    message.setText(body);


    Transport transport = session.getTransport("smtp");


    transport.connect(host, from, pass);
    transport.sendMessage(message, message.getAllRecipients());
    transport.close();

}
catch (AddressException ae) {
    ae.printStackTrace();
}
catch (MessagingException me) {
    me.printStackTrace();
  }
 }
} 

Answer 4

我有同样的问题。将主机 smtp.gmail.com 更改为 ip 74.125.133.109，现在它运行良好。