How to multiple class add on contact form 7 submit button

Also CF7 used to have bug: if you put "class:" after "Send" nothing is added.

Have also just discovered if you put classes after a placeholder it doesn't work for some reason but putting it before does:

[text* your-name class:ast-col-xs-12 class:ast-col-sm-12 class:ast-col-md-6 class:ast-col-lg-6 placeholder "e.g. Joe Bloggs"]

If I remember correctly, you need to add the class attribute to each one.

Try this instead:

[submit class:btn class:btn-main class:btn-lg "Send"]