This is the only address. No form — there is no backend behind one — and nothing to request a quote for. Every other page links here instead of carrying its own copy, so it can only ever be wrong in one place.
Plain email; attachments are fine. Writing about a specific page? Paste its URL. Each report ships the verifier that produced its numbers, so you can run it before you write — and if it disagrees with the page, that is the most useful message you could send.
Three kinds of message get a real answer. Being specific is what makes a reply possible; a one-line introduction usually cannot be answered with anything but another one.
Name the artifact and the one step you doubt, then send the input you expect it to fail on. A reproducible counterexample beats agreement here, and a refutation is published like any other result — with your name on it if you want it there.
Say which result, and what you would do with it. The top rung of the ladder used here is reserved for work a named human reviewer has tried to break — the one thing one person cannot supply.
Say what you compute today, and what would go wrong if the answer were quietly off by a little. That is far more answerable than "what do you do", and the reply points at a page you can re-run rather than at a brochure.
Not a support channel. Nothing here is a product, so there is no queue, no SLA, no on-call and no ticket to escalate. Replies come from one person between other work: often slow, never guaranteed. Treat what you send as ordinary correspondence unless you say otherwise.