bug#51733: 27.1; Detect impossible email addresses better

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: rpluim@gmail.com,  51733@debbugs.gnu.org
> Date: Wed, 19 Jan 2022 14:10:11 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > E.g., what if someone sends me a citation from someone else's
> > email, and I want to textsec-check that citation?  Chances are the
> > citation will not include RFC2047 encoded addresses.
> 
> You can, of course, add all kinds of things to try to gues whether other
> things in other places in Emacs are suspicious or not, but that is not
> what these functions I've written do.

I don't understand this stubborn opposition to provide better, more
general APIs to our users.  textsec.el is not an application, it is
infrastructure applications should use to provide user-level features.
So any application-level decisions, like at what level to detect
suspicious addresses, is not textsec's bloody business to make!