Code edits to send HTML email via admincp in vBulletin

[admin]

This works on vBulletin 3.7.x and 3.8.x

Step 1:
In admincp/email.php find:

print_textarea_row($vbphrase['message_email'], 'message', '', 10, 50);

Directly below it place:

print_yes_no_row('Send HTML Email?', 'sendhtml', 0);

Step 2:
In admincp/email.php find:

construct_hidden_code('test', $vbulletin->GPC['test']);

Directly below it place:

construct_hidden_code('sendhtml', $_POST['sendhtml']);

Step 3:
In includes/class_mail.php find:

$headers .= 'Content-Type: text/plain' . iif($encoding, "; charset=\"$encoding\"") . $delimiter;

and replace with:

if($_POST['sendhtml'])  {
  $headers .= 'Content-Type: text/html' . iif($encoding, "; charset=\"$encoding\"") . $delimiter;
}else{
  $headers .= 'Content-Type: text/plain' . iif($encoding, "; charset=\"$encoding\"") . $delimiter;
}