Java Mail: Exception when sending email

First time working with java mail. I’m following this tutorial but I already fail at sending a basic message and I get a very strange error:

java.util.ServiceConfigurationError: javax.mail.Provider: Provider com.sun.mail.imap.IMAPProvider not a subtype

Strange because I’m not using IMAP anywhere in my code:

Properties mailProps = new Properties();
mailProps.put("mail.transport.protocol", "smtp");
mailProps.put("mail.host", "smtp.mydomain.com");
mailProps.put("mail.from", "[e-mail]");
mailProps.put("mail.smtp.port", "25");     

Session session = Session.getDefaultInstance(mailProps);
SMTPMessage m = new SMTPMessage(session);
MimeMultipart content = new MimeMultipart();
MimeBodyPart mainPart = new MimeBodyPart();
mainPart.setText("test");
content.addBodyPart(mainPart);  
m.setContent(content);
m.setSubject("Demo message");

m.setRecipient(RecipientType.TO, new InternetAddress("[e-mail]"));
Transport.send(m);

The error happens on last line (send). I know the smtp server is correct and working.

Any advice why this happens and how I can solve it?

EDIT: obviously the addresses/hosts are changed here and I’m using real ones that work in the actual code.

Answer

it turns out I was running into multiple issues:

1. Issue with tutorial

It uses com.sun.mail.smtp.SMTPMessage but in my case that doesn’t work but using javax.mail.internet.MimeMessage works fine.

2. Root cause of error

Above code runs within a 3rd party eclipse based application and they seem to interfere with each other. The solution for this can be found here:

Thread t =  Thread.currentThread();
ClassLoader ccl = t.getContextClassLoader();
t.setContextClassLoader(session.getClass().getClassLoader());
try {
    Transport.send(m);
} finally {
    t.setContextClassLoader(ccl);
}

Adjusting the code accordingly make it work.