Dizzie,
A caveat, I run my own servers so I have control over the setup, what is used or usable etc etc.
That said, the setup that produced the desired html newsletters is as follows:
Server - Ubuntu Linux 6.06 - 2.6.15-27
PHP 5.1.2
MySQL 5.0.22
Mail - Postfix, 8bit Mime enabled.
Zen Cart 1.3.7
In Admin, mail transport set to PHP, email linefeeds LF, use mime, send email, use archiving and friendly errors all set to true, as well as 'must send from known domain. Admin format set to HTML.
Editor used is FCKEditor.
What prompted my investigation was that the newsletters were always received as 7bit mime, despite it being set to 8bit, and that my mail server is also set to 8bit, and only reformats to 7 if the destination server cannot handle 8.
Since I was getting the mail off the same server Zen Cart was using, this seemed strange, and led to the discovery that newsletters were not picking up the transport method setting.
I have tested it with both Newsletter only subscriptions mod installed and without, and it seems to work fine, and tested to Gmail, Hotmail and some fairly strictly setup Outlook clients. All work.
With regard to how to test it, I've attached a functions_email.php which has been modified to force html on the admin user. i.e. if you select the administrator from the newsletter audience select, it will send the html newsletter, not the text version.
It is a brute force hack, just the 2 following pieces of dreadful code added:
$adm = 0;
$fndadm = 'ADMIN';
$adm = strpos($to_name,$fndadm);
if ($adm===false) $adm=0;
else $adm=1;
if ($adm > 0){
$customers_email_format = 'HTML';
}
if ($adm > 0) {
$mail->IsHTML(true);
$mail->Body = $email_html;
$mail->AltBody = '';
but it at least allows you to send test newsletters to admin.
I honestly don't remember whether I wrote this, or found it somewhere, so if I have appropriated someone elses code, I apologise, please let me know, and I will gladly give acknowledgement.
If you use the newsletter subs mod, shout and I'll send the file.
Rgds,
Chuck