How can i add "focus" direcrtly by the style tag in html?

HTML & CSS
1

How can i add “focus” direcrtly by the style tag in html?
for ex: (I cant use stylesheet or javascript for this issue, since its inside mail)

<a href="#" style="a:focus { border: 1px solid #000; }">CLICK ME TO SEE THE BOUNDRIES</a>
2

You can’t do that (that is, insert pseudo classes inline). When you say “inside mail”, do you mean inside an HTML email?