Com sun mail util mailconnectexception couldn t connect to host

A classic Java email error!

The MailConnectException with the message "Couldn't connect to host" usually occurs when the Java Mail API is unable to establish a connection to the mail server. Here are some common causes and solutions:

1. Check your mail server settings:
   • Verify that your mail server settings are correct, including the host name, port number, username, and password.
   • Make sure that the mail server is running and accessible.
2. Network connectivity issues:
   • Check your network connection to ensure that you can reach the mail server.
   • Verify that your firewall or antivirus software is not blocking the connection.
3. Mail server authentication issues:
   • Ensure that your username and password are correct and valid.
   • Check if the mail server requires SSL/TLS encryption and update your Java Mail API settings accordingly.
4. Java Mail API configuration:
   • Verify that you have correctly configured the Java Mail API, including the mail host, port, and authentication settings.
   • Check the Java Mail API documentation for specific configuration requirements.
5. SSL/TLS issues:
   • If your mail server requires SSL/TLS encryption, ensure that you have enabled it in your Java Mail API settings.
   • Check if your Java Mail API version supports SSL/TLS encryption.
6. Timeout issues:
   • Increase the timeout value in your Java Mail API settings to allow for a longer connection attempt.
   • Check if your mail server has a timeout setting that is causing the connection to fail.

Here's an example of how you can configure the Java Mail API to connect to a mail server:

import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class SendEmail {
    public static void main(String[] args) {
        Properties props = new Properties();
        props.put("mail.smtp.host", "your.mail.server.host");
        props.put("mail.smtp.port", "your.mail.server.port");
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");

        Session session = Session.getInstance(props, new Authenticator() {
            @Override
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication("your.username", "your.password");
            }
        });

        try {
            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress("[email protected]"));
            message.setRecipients(Message.RecipientType.TO, InternetAddress.parse("[email protected]"));
            message.setSubject("Test Email");
            message.setText("Hello, this is a test email.");

            Transport.send(message);
            System.out.println("Email sent successfully!");
        } catch (MessagingException e) {
            System.out.println("Error sending email: " + e.getMessage());
        }
    }
}

Make sure to replace the placeholders (your.mail.server.host, your.mail.server.port, your.username, your.password, [email protected], and [email protected]) with your actual mail server settings and email addresses.