bug#51733: 27.1; Detect impossible email addresses better

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: 51733@debbugs.gnu.org,  jidanni@jidanni.org
> Date: Wed, 19 Jan 2022 14:55:35 +0100
> 
> But this should be, but isn't currently:
> 
> (textsec-domain-suspicious-p "Сгсе.ru")
> => nil

Why? .ru is a top-level domain, it doesn't affect what should be
before the dot, I think?

If you replace "Сгсе.ru" with "Cгсе.ru", you do get a warning.

> Is that what they mean here?

I'm not sure I understand the purpose of finding which scripts
"contain a whole-script confusable with a string X".  What are we
supposed to do with the resulting list?