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Re: [ietf-smtp] [dispatch] BCP proposal: regular expressions for Internet Mail identifiers

2016-03-30 23:29:25
On Tue, 29 Mar 2016 15:38:59 -0400, John C Klensin said:

Actually five families if you want to do a comprehensive job:

 - 5321, possibly with nods to its predecessors
 - 5322 which, as you point out, is not the same as 5321
      (and most, if not all, of the differences are
 - the EAI family
 - the base DNS spec family, as updated

And the corner cases when they don't agree. Consider  - how long did *that* wart get debated? :)

Those of us who were around for RFC1341 can look at the following,
and weep, and ponder what failure modes the authors of this would have
managed if they had *both* an ABNF and a regexp provided to work from,
*even if they were semantically the same*...

% egrep 'X-Mail|alt' bad.mailfile
X-Mailer: IBM Notes Release 9.0.1FP2 SHF37 August 25, 2014
Content-Type: multipart/alternative; boundary="=_alternative  
--=_alternative 002EDD9148257F79_=
--=_alternative 002EDD9148257F79_=
--=_alternative 002EDD9148257F79_=--

(Hint:  You'll probably need a fixed-space font and a lot of pondering - the
above cost me close to 10 days of aggravation trying to figure out why one
vendor's support emails were consistently getting eaten by my procmail
filters, before I finally spotted it...)

This is why we can't have nice things....

Oh, and those who want to tempt the Lovecraftian regexp elder gods should
ponder the following:

(If that doesn't make Sean reconsider, *nothing* will... :)

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