bug#51733: 27.1; Detect impossible email addresses better

[Lars Ingebrigtsen]

I'm not quite sure how noticeable we should be making suspicious things.
With the following test file with `M-x eww-open-file':

The ⚠️ will obviously be customiseable, but is this generally the amount
of attention we should be aiming for?  The mouseover on the ⚠️s has the
explanation for the suspicion -- we could also output that text into the
buffer, but I think that's overkill.

Anybody have an opinion?  

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no
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