PHP Mail: Diacritics and Special Characters in Name and Subject are not displayed

Generally, the participating programs and servers only understand ASCII characters in the header of the e-mail. The letters from A to Z fall in this area, the diacrits, umlauts or a wide range of special characters not.

For this reason, you must separately encode the UTF-8 characters within the header:

$text = 'Subject with Ä, Ö and Ü';
$sunject= '=?UTF-8?B?'.base64_encode($text).'?=';

Since this topic is more extensive, I wrote an article about the UTF-8 Header in the PHP-Mail function. In this article you will find an explanation of this line of code as well as a complete example of what a function might look like to prepare and send such a encoded mail.
2019-03-08 at 17:48