Re: Reply-prefix ("Re:") default regex

[Steinar Bang <sb@dod.no>]

>>>>> Paul van der Walt <paul@denknerd.org>:

> I recently ran into an issue where a French speaker i was communicating
> with had "Re : ..." as their reply subject prefix (note the leading
> space before the colon).  This quickly ended up with us bouncing emails
> around with such lovely subject lines as "Re: Re : Re: Re : Re: ...", et
> cetera, ad infinitum.  This phenomenon, of surrounding certain
> punctuation marks with extra spaces, turns out to be A Thing™ in French
> writing [0].  I discovered that by making a very small modification to
> the term `message-subject-re-regexp`, the problem was solved for me,
> locally (it's in my configuration files ATM).  But since this might be
> something that's useful to others, i threw a patch together, attached.

On a side note I have solved this outside of Gnus in procmail with this in my
.procmailrc:

#
# Fix Subject RE/SV/AW line for MSExchange/MSMail/MSOutlook
# Also fix Subject field for Norwegian android mailer ("Vedr").
# No X-Mailer field to rely on, unfortunately!
# Remove MSE quotes of type "'Real Name'"
#
:0 fhw
| /usr/bin/perl -ne "s/\?[Ww]indows-1252\?/?iso-8859-1?/g; s/^(Subject:)\s+(S[Vv]:\s*|AW:\s*|Ad:\s*|Vedr:\s*|R[eE](\(\d+\))?:\s*)+/\1 Re: /g;s/^(Subject:)\s+(=\?((iso|ISO)-8859-1|us-ascii)\?Q\?)((S[Vv]|AW|Ad|R[eE](\(\d+\))?)(:|=3[Aa])_*)+/\1 \2Re:_/g; s/\042\'([^\']*)\'\042/\042\1\042/g ; print"

As this regular expression shows there seems to be a great deal of
creativity when it comes to messing up subject headers.  Everything
matched here has been encountered in the wild.