Java邮件 : Could not connect to SMTP server

Question

以下代码会导致错误。请帮助我理解出了什么问题。

import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;
public class SendMail
{
  public static void main(String [] args)throws MessagingException
  {
    SendMail sm=new SendMail();
     sm.postMail(new String[]{"abc@yahoo.co.in"},"hi","hello","xyz@gmail.com");
   }

public void postMail( String recipients[ ], String subject, String message , String from) throws MessagingException
{
    boolean debug = false;

     //Set the host smtp address
     Properties props = new Properties();
     props.put("mail.smtp.host", "webmail.emailmyname.com");

    // create some properties and get the default Session
    Session session = Session.getDefaultInstance(props, null);
    session.setDebug(debug);

    // create a message
    Message msg = new MimeMessage(session);

    // set the from and to address
    InternetAddress addressFrom = new InternetAddress(from);
    msg.setFrom(addressFrom);

    InternetAddress[] addressTo = new InternetAddress[recipients.length]; 
    for (int i = 0; i < recipients.length; i++)
    {
        addressTo[i] = new InternetAddress(recipients[i]);
    }
    msg.setRecipients(Message.RecipientType.TO, addressTo);


    // Optional : You can also set your custom headers in the Email if you Want
    msg.addHeader("MyHeaderName", "myHeaderValue");

    // Setting the Subject and Content Type
    msg.setSubject(subject);
    msg.setContent(message, "text/plain");
    Transport.send(msg);
}
}

Exception:
<pre>
com.sun.mail.smtp.SMTPSendFailedException: 450 smtpout04.dca.untd.com Authentication required

    at com.sun.mail.smtp.SMTPTransport.issueSendCommand(SMTPTransport.java:1829)
    at com.sun.mail.smtp.SMTPTransport.mailFrom(SMTPTransport.java:1368)
    at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:886)
    at javax.mail.Transport.send0(Transport.java:191)
    at javax.mail.Transport.send(Transport.java:120)
    at SendMail.postMail(SendMail.java:52)
    at SendMail.main(SendMail.java:10)

Answer 1

异常消息中的“需要身份验证”表明目标 SMTP 服务器要求您登录(可能通过 TLS 或 SSL)。直到几年前，这种情况在 SMTP 服务器上并不常见(这是一种反垃圾邮件措施)，因此很容易被忽视。

致authenticate with JavaMail :

To use SMTP authentication you'll need to set the mail.smtp.auth property (see below) or provide the SMTP Transport with a username and password when connecting to the SMTP server. You can do this using one of the following approaches:

• Provide an Authenticator object when creating your mail Session and provide the username and password information during the Authenticator callback.

  Note that the mail.smtp.user property can be set to provide a default username for the callback, but the password will still need to be supplied explicitly.

  This approach allows you to use the static Transport send method to send messages.

• Call the Transport connect method explicitly with username and password arguments.

This approach requires you to explicitly manage a Transport object and use the Transport sendMessage method to send the message. The transport.java demo program demonstrates how to manage a Transport object. The following is roughly equivalent to the static Transport send method, but supplies the needed username and password:

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

tr.connect(smtphost, username, password);

msg.saveChanges(); // don't forget this

tr.sendMessage(msg, msg.getAllRecipients());

tr.close();