ok im just assuming htmlMimeMail is the page where the mail is sent, im also assuming you are not using smtp.
ok find line 668-672 of htmlMimeMail.php it should look like this:
if (!empty($this->return_path)) {
$result = mail($to, $subject, $this->output, implode(CRLF, $headers), '-f' . $this->return_path);
} else {
$result = mail($to, $subject, $this->output, implode(CRLF, $headers));
}
now replace the chunk of text with this:
if (!empty($this->return_path)) {
$result = mail($to, $subject, eval("$this->output"), implode(CRLF, $headers), '-f' . $this->return_path);
} else {
$result = mail($to, $subject, eval("$this->output"), implode(CRLF, $headers));
}