https://blame.email/ https://blame.email/ is a website that does this. I wrote a Lua checker for rspamd that bypasses the spam filter if the address is "signed"

https://blame.email/ https://blame.email/ is a website that does this. I wrote a Lua checker for rspamd that bypasses the spam filter if the address is "signed". I also have a bookmarklet that generates a signed address and inserts it into the current text field.