Hi, found another issue after upgrading from 1.5.x to 1.6.8:

The email notifications on new comments are now unreadable, base64 encoded blob, instead of plain ascii text like they used to, whenever someone posts a new comment.

Of course we don't recommend doing large version jumps from 1.5.x (especially if not the last 1.5.x) to 1.6.8 for a reason. You jumped over three years of updates on one go.

There have been lots of changes and one includes a database encoding change to support utf8mb4 encoding (the actual real utf8 MySQL didn't formerly). That may affect here or some wrong settings. Or your server does not support utf8 or doesn't have the multibyte or iconv extension. Setup will tell.

Found the bug, the email headers are not properly separated in the send_mail member function of class-utf8, email headers requires "\r\n" not just "\n":

lib/class-utf8.php

class-utf8:end_mail
line 713:

    if ($additional_headers != '')
        $additional_headers .= "\r\n";

    $additional_headers .=
                    "Mime-Version: 1.0\r\n" .
                    "Content-Type: text/plain; charset=UTF-8\r\n" .
                    "Content-Transfer-Encoding: base64";

Weird, that for sure has not been change for ages. Very old library we probably will retire in the near future (we should be using the mb_mail() function if available instead of this). Anyway, please send a pull request with the change via GitHub.

Never mind, I will add the change myself later, probably next year.

Change is now on github in 1.7a.