How to set an umlaut ü in the mail subject

Question

I need to generate German e-mails which contain umlaut characters. In the e-mail itself this works perfectly, but not in the subject of the e-mail. I've tried many different umlaut letters and they all seem to work except for the ü. I also tried different mail libraries (HTMLMimeMail & PHPMailer) and they both fail at this:

$mail = new htmlMimeMail();
$mail->setTextEncoding("base64");
$mail->setHTMLEncoding("base64");
$mail->setTextCharset("UTF-8");
$mail->setHTMLCharset("UTF-8");
$mail->setHeadCharset("UTF-8");
$mail->setSMTPParams(mailinglist_smtp_host,mailinglist_smtp_port);
$mail->setHtml("test");
$mail->setFrom("[email protected]");    

$mail->setSubject("The ï, ö, ë, ä, and é work, but when adding the ü it doesn't");

$recipients[] = "[email protected]";    
$mail->send($recipients);

&

$mail = new PHPMailer();
$mail->IsMail();
$mail->FromName = 'test';
$mail->From = '[email protected]';
$mail->AddAddress("[email protected]");
$mail->Subject = "The ï, ö, ë, ä, and é work, but when adding the ü it doesn't";
$mail->Body = "test";    
$mail->Send();

Can anyone help me find the source of and the solution to this problem?

Answer 1

You should quoted-printable encode the subject header.

Like this:

$mail->Subject = "=?UTF-8?Q?" . quoted_printable_encode("The ï, ö, ë, ä, and é work, but when adding the ü it doesn't") . "?=";

Quoted printable encode in PHP: http://www.php.net/manual/en/function.quoted-printable-encode.php

Edit: $mail->CharSet = "UTF-8"; did the job.