An email client (or server), that would, upon receiving an email from a previously unrecognized source, send an email back with a captcha style problem to be solved by the email's originator prior to making the email visible to a human recipient.
-- theircompetitor, Jan 27 2020

Mailwasher https://www.mailwasher.net/
Mailwasher is not in any way associated with or afilliated to or Assimilated by BorgCo. [8th of 7, Jan 27 2020]

Mailwasher <link> does something a bit like this ... it allows you to preview your mail and bounce it if you don't like the preview.

The bounce message can include some human-readable instructions like "Add the phrase 'Happy Frost Biscuit' to the subject line to permit delivery'" . Then if it reappears with the nonsense phrase, you know it's genuine.
-- 8th of 7, Jan 27 2020


This sounds like something, like an autoresponder, that each of us could run, by using Gmail API to change message flags, and a verification endpoint hosted somewhere, even on our own websites. [+]
-- Mindey, Jan 28 2020


YES!!!
-- blissmiss, Jan 29 2020



random, halfbakery