Email Letterhead

Hi all,

I'm wondering if anyone was able to create a letterhead using CSS or Javascript for all emails sent from the knack app? I have more than 30 forms and every time I change something in the email notification, I need to go back and change it in all the forms. Sometimes I have more than one email in the same form with just a small difference. Having a letterhead would really save me a lot of time copying and pasting the customized emails to every single form.

Please help me in this :( and thank you in advance.