bug#51733: 27.1; Detect impossible email addresses better

[Robert Pluim]

>>>>> On Wed, 19 Jan 2022 11:27:57 +0100, Lars Ingebrigtsen <larsi@gnus.org> 
>>>>> said:

    Lars> Robert Pluim <rpluim@gmail.com> writes:
    >> OK, but the error message could be better, no?

    Lars> Sure, but what?  (And it's not an error message, it's information 
about
    Lars> something that looks like it might be odd.)

    Lars> Summarising Unicode® Technical Standard #39 in one line isn't easy.

    Lars> We can go all vague, like "Something is wrong", or we can go long, 
like
    Lars> "It's not all-ASCII, and it's not single script, and it's not a 
mixture
    Lars> of arabic armenian bengali bopomofo devanagari ethiopic georgian
    Lars> gujarati gurmukhi hangul han hebrew hiragana katakana kannada khmer 
lao
    Lars> malayalam myanmar oriya sinhala tamil telugu thaana thai tibetan 
latin,
    Lars> and it not a latin/han/korea/japan mixture".  (And I probably forgot
    Lars> some bits.)

How about "Contains suspicious characters or mix of characters"? That
would at least point users in the right direction.

Robert
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