Okay I hacked myself a solution but this will need to be reapplied every time Email Users is updated. Basically I changed email-users.php and changed this:
if ('html' == $type) {
if (mailusers_get_add_mime_version_header() == 'true')
$headers[] = 'MIME-Version: 1.0';
$headers[] = sprintf('Content-Type: %s; charset="%s"', get_bloginfo('html_type'), get_bloginfo('charset')) ;
$mailtext = "<html><head><title>" . $subject . "</title></head><body>" . $message . $footer . "</body></html>";
} else {
if (mailusers_get_add_mime_version_header() == 'true')
$headers[] = 'MIME-Version: 1.0';
$headers[] = sprintf('Content-Type: text/plain; charset="%s"', get_bloginfo('charset')) ;
$message = preg_replace('|&[^a][^m][^p].{0,3};|', '', $message);
$message = preg_replace('|&|', '&', $message);
$mailtext = wordwrap(strip_tags($message . "\n" . $footer), 80, "\n");
}
to this …
if ('html' == $type) {
if (mailusers_get_add_mime_version_header() == 'true')
$headers[] = 'MIME-Version: 1.0';
$mailtext = $message;
} else {
if (mailusers_get_add_mime_version_header() == 'true')
$headers[] = 'MIME-Version: 1.0';
$headers[] = sprintf('Content-Type: text/plain; charset="%s"', get_bloginfo('charset')) ;
$message = preg_replace('|&[^a][^m][^p].{0,3};|', '', $message);
$message = preg_replace('|&|', '&', $message);
$mailtext = wordwrap(strip_tags($message . "\n" . $footer), 80, "\n");
}
And now it works.
An option to omit the HTML-Body-Wrapper would be better!