Correct, I'm adding my email via the form builder. Then, a month or so later, it disappears.
Now, having been watching it for some time, the email address is staying, but, for the life of me, it won't send an email when i use the form. from my computer or others.
It's been 5 days now and no emails.
I had to download the smtp email check plugin and now it's working.
Oddly, I've setup accounts for others using this style of contact form and they all report theirs is working. Also, my theme builder mentions it's not an issue with the theme.
I've also logged out of jetpack and then back in.