you can do it like this with raw javascript
<html>
<body>
<form id="my_form" method="post" action="mailto://test@test.com">
<a href="javascript:{}" onclick="document.getElementById('my_form').submit();">submit</a>
</form>
</body>
</html>
For those asking why I have a href element in my anchor tag, its because it’s a compulsory part of an anchor tag, it may well work without but it’s not to spec. So if you want to guarantee rendering etc you must give the engine a fully formed tag. So the above achieves this. You will see href="#" used sometimes but this is not always wanted as the browser will change the page position.