JavaMail - multiple senders

Question

I have a simple javamail class to send emails through SMTP. It works as long as I only send emails from one address. If I try using another address, it raises this exception for some reason:

com.sun.mail.smtp.SMTPSendFailedException: 550 5.1.0 Use your own address, please.

Here's my class:

public class EmailSender {
    private static final String HOST = "xxxx.xxxxxx.xx";
    private static final String PORT = "xx";

    public static boolean sendMail(String from, String to, String pass, String subject, String text) {
        Properties properties = new Properties();

        properties.setProperty("mail.smtp.host", HOST);
        properties.setProperty("mail.smtp.port", PORT);
        properties.setProperty("mail.smtp.auth", "true");
        properties.setProperty("mail.user", from);
        properties.setProperty("mail.password", pass);

        Session session = Session.getDefaultInstance(properties, new CustomAuthenticator(from, pass));

        try {
            MimeMessage message = new MimeMessage(session);
            message.setFrom(new InternetAddress(from));
            message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));
            message.setSubject(subject);
            message.setText(text);

            Transport.send(message);

            return true;
        } catch (MessagingException e) {
            e.printStackTrace();
            return false;
        }
    }
}

In case you're wondering, the CustomAuthenticator class looks like this:

public class CustomAuthenticator extends Authenticator {
    private String user;
    private String pw;

    public CustomAuthenticator(String username, String password) {
        super();
        this.user = username;
        this.pw = password;
    }

    public PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(user, pw);
    }
}

Answer 1

So I found out that the solution is to use the SMTPTransport class.

public class EmailSender {
    private static final String HOST = "xxxx.xxxxxx.xx";
    private static final String PORT = "xx";

    public static boolean sendMail(String from, String to, String pass, String subject, String text) {
        Properties properties = new Properties();

        properties.setProperty("mail.smtp.port", PORT);
        properties.setProperty("mail.smtp.auth", "true");

        Session session = Session.getDefaultInstance(properties, new CustomAuthenticator(from, pass));

        try {
            MimeMessage message = new MimeMessage(session);
            message.setFrom(new InternetAddress(from));
            message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));
            message.setSubject(subject);
            message.setText(text);

            SMTPTransport tp = (SMTPTransport) session.getTransport();
            tp.connect(HOST, from, pass);
            tp.sendMessage(message, message.getAllRecipients());
            tp.close();

            return true;
        } catch (MessagingException e) {
            e.printStackTrace();
            return false;
        }
    }
}

Answer 2

Your server won't let you use an address that's not yours. Depending on your server, there may be a way to convince it that the other address is also yours. Normally "yours" means "the address associated with the account you used when you logged in".