The charset used to send the newsletter might not necessarily be the charset that is used by the email reader. For example, in a newsletter I sent to myself, the ü in einfügen was changed to ü so in my email reader I saw einfügen (UTF-8) instead of einfügen (ISO-8859-1) though my email reader gave me the following message:
This message was written in a character set other than your own. If it is not displayed correctly, click here to open it in a new window.
Once clicked, the word einfügen appeared correctly. That said, if you know what charset you want to use, look for the following code in the gaz_class_process.php file:
Code:
$subject = $this->mailobj->encode_email_header(unhtmlspecialchars($subject, $unicode_decode), $encoding, false, false);
And beforehand you can set what charset you would like to try.