CSS Prefixing

Hello everyone. I have created a repository for an HTML email specification
on Github (https://github.com/W3CGHtmail/html-email-spec). My plan is to
start by discussing different points, see where everyone stands, and then
start writing a draft.

I've opened a discussion about CSS Prefixing (
https://github.com/W3CGHtmail/html-email-spec/issues/1). I've made tests
across ten webmails to see what practices are currently in place.

What recommandations should we bring to webmails for CSS prefixing ? Feel
free to answer on Github or here.

-- Rémi