Given that you are dealing with email, I'd run
wp_kses() with a very limited
$allowed_html array similar to this sample from the Codex:
'a' => array(
'href' => array(),
'title' => array()
'br' => array(),
'em' => array(),
'strong' => array(),
HTML rendering is even more squirrelly in email readers than browsers (and there are a lot more readers to worry about) so you want to be very careful what you allow. That is going to mean that you will need to truncate the visual option in your editor too. I am sure there are posts here about doing that.
All in all, I'll consider using a very simple markdown and skipping the complexity of the editor completely.