What do you mean "guarantees the origin of the email" though? That it was you who sent it? That you're allowed to send emails from mymail@example.com? The latte

What do you mean "guarantees the origin of the email" though? That it was you who sent it? That you're allowed to send emails from mymail@example.com? The latter has been solved for some time; the first one is harder, but solvable through GPG or S/MIME, but few seems to have any interest in implementing it. That won't stop anyone from creating a new email address (or mail server) that sends out spam though.