java - UTF-8 charset doesn't work with javax.mail

Question

I have used Java Mail API, for sending emails. I am using a contact formular to send the input, which has to be send to a specific email.

The email is send without problems, though I am a danish guy, and I am therefore in need of three danish characters which is '?', '?' and '?', in the subject and the email text.

I have therefore seen that I can use UTF-8 character encoding, to provide these characters, but when my mail is send I only see some strange letters - '?|', '??' and '?￥' - instead of the danish letters - '?', '?' and '?'.

My method to send the email is looking like this:

public void sendEmail(String name, String fromEmail, String subject, String message) throws AddressException, MessagingException, UnsupportedEncodingException, SendFailedException
{
    //Set Mail properties
    Properties props = System.getProperties();
    props.setProperty("mail.smtp.starttls.enable", "true");
    props.setProperty("mail.smtp.host", "smtp.gmail.com");
    props.setProperty("mail.smtp.socketFactory.port", "465");
    props.setProperty("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
    props.setProperty("mail.smtp.auth", "true");
    props.setProperty("mail.smtp.port", "465");
    Session session = Session.getDefaultInstance(props, new javax.mail.Authenticator() {
        @Override
        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication("my_username", "my_password");
        }
    });

    //Create the email with variable input
    MimeMessage mimeMessage = new MimeMessage(session);
    mimeMessage.setHeader("Content-Type", "text/plain; charset=UTF-8");
    mimeMessage.setFrom(new InternetAddress(fromEmail, name));
    mimeMessage.setRecipient(Message.RecipientType.TO, new InternetAddress("my_email"));
    mimeMessage.setSubject(subject, "utf-8");
    mimeMessage.setContent(message, "text/plain");

    //Send the email
    Transport.send(mimeMessage);
}

Please help me find out how I can correct this 'error'.

Answer 1

For all e-mails

There are a couple of system properties related to mailing, that can probably simplify your code. I am talking about this specific property actually: "mail.mime.charset".

The mail.mime.charset System property can be used to specify the default MIME charset to use for encoded words and text parts that don't otherwise specify a charset. Normally, the default MIME charset is derived from the default Java charset, as specified in the file.encoding System property. Most applications will have no need to explicitly set the default MIME charset. In cases where the default MIME charset to be used for mail messages is different than the charset used for files stored on the system, this property should be set.

As you can read above, by default there is no value for the mail.mime.charset and the file encoding (file.encoding property) is used.

For a specific e-mail

However, if you want to specify a specific encoding for a specific e-mail, then you should probably use the 2 parameter setSubject(subject,charset) and setText(text,charset) methods.

If that doesn't work, then probably your input is already corrupted before it reached this point. In other words, you probably used the wrong encoding to collect your data.

Mime types are complicated

The setContent(content, "UTF-8") (as other sources claim) will just not work. Just look at the signature of this method: setContent(Object content, String mimetype). Mime type and charset are 2 totally different things. Imho, you should really be using one of the setText(...) methods with a charset parameter.

But if you persist in using a mimetype to set the charset setContent(content,mimetype), then use the correct format. (not just "UTF-8", but something like "text/plain; charset=UTF-8"). But more importantly, be aware that every mime-type has its own way of handling charsets.

• As specified in RFC-2046 the default charset for text/plain is US-ASCII, but can be overruled with an additional charset parameter.
• However, in RFC-6657 makes clear that the text/xml type determines the charset using the content of the message. The charset parameter will just be ignored here.
• And in RFC-2854 is stated that text/html should really always specify a charset. But if you don't, then it will use ISO-8859-1 (=Latin-1).