Javamail changing charset of subject line

I am using Javamail (javax.mail) to send mails. I successfully adjusted contents of my mail as utf-8. However I could not set subject line as a utf-8 encoded string.

I tried even

mail.setSubject(new String(subject.getBytes("utf-8"), "utf-8"));

on subject however it still sends as Cp1252. Example headers from mail are given below:

Any ideas?

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You should use setSubject(String subject, String charset) which is a convenient function for this purpose.

Session session=Session.getDefaultInstance(new Properties());
MimeMessage mimeMsg= new MimeMessage(session);
String subject="Herr Müller reist nach \u0141\u00f3d\u017a.";
mimeMsg.setSubject(subject,"utf-8");
System.out.println(subject);
System.out.println(mimeMsg.getHeader("Subject")[0]);

In MimeUtility it is said:

There are a set of methods to encode and decode MIME headers as per RFC 2047. Note that, in general, these methods are not needed when using methods such as setSubject and setRecipients; JavaMail will automatically encode and decode data when using these "higher level" methods. The methods below are only needed when maniuplating raw MIME headers using setHeader and getHeader methods.

From my point of view, Message.setSubject should be the entry point for this purpose.

The cp1252 in your subject encoding shows up, because it is your standard encoding on your platform.

Your posted example is the "result" of

mail.setSubject(MimeUtility.encodeText(subject, "cp1252", "Q"));`

Solved.

mail.setSubject(MimeUtility.encodeText(subject, "utf-8", "B"));

solves it and sends utf-8 encoded mail subjects. \n/

the legal values for "encoding" are "Q" and "B"... The "Q" encoding is recommended for use when most of the characters to be encoded are in the ASCII character set; otherwise, the "B" encoding should be used.

See https://www.rfc-editor.org/rfc/rfc2047.

Problem solved!

mail.setSubject(MimeUtility.encodeText(subject, "utf-8", "B"));

solves it and sends utf-8 encoded mail subjects.

Why there is that "B" why there isn't ISO-something?

The MimeMessage.setSubject(String subject, String charset) method will solve the problem: mimeMsg.setSubject(subject,"utf-8");

This is an updated link. Previous documentation link was dismissed by Oracle after Oracle bought the Sun.

I ran into a similar problem with Apache Camel Mail, which uses Java Mail. Setting

exchange.setProperty(Exchange.CHARSET_NAME, "UTF-8");

before routing to SMTP, solved the problem.

Solved.

import static java.nio.charset.StandardCharsets.*; 

byte[] bytes = subject.getBytes(ISO_8859_1);
subject = new String(bytes, UTF_8);

mail.setSubject(subject);