[exim-dev] [Bug 485] Exim mistakenly prohibits underscore (_…

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Author: bug485
Date:  
To: exim-dev
Subject: [exim-dev] [Bug 485] Exim mistakenly prohibits underscore (_) in /HELO/EHLO commands
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http://www.exim.org/bugzilla/show_bug.cgi?id=485





------- Comment #1 from graeme@??? 2007-03-16 08:30 -------
On Fri, 2007-03-16 at 03:52 +0000, exim@??? wrote:
> 2007-03-11 21:11:21 rejected HELO from gfhowalogon.glensfallshosp.org
> [64.80.241.66]: syntactically invalid argument(s):
> gfh_exchange.glensfallshosp.org
>
> Following RFC 1425, EHLO is:
>                ehlo-cmd ::= "EHLO" SP domain CR LF
> 'domain' is defined in RFC822:
> domain      =  sub-domain *("." sub-domain)
> sub-domain  =  domain-ref / domain-literal
> domain-ref  =  atom
> atom        =  1*<any CHAR except specials, SPACE and CTLs>
>      specials    =  "(" / ")" / "<" / ">" / "@"  ; Must be in quoted-
>                  /  "," / ";" / ":" / "\" / <">  ;  string, to use
>                  /  "." / "[" / "]"              ;  within a word.
> CHAR        =  <any ASCII character>        ; (  0-177,  0.-127.)
> Since underscore is not in specials, nor is it a SPACE or CTL, it is not
> prohibited. Hence, by definition, it is not "syntactically invalid". Or is
> there something I'm missing?


RFC1425 obsoleted by 1651, then by 1869, then by 2821. From RFC2821:

The argument field contains the fully-qualified domain name of the SMTP
client if one is available.

An FQDN may not contain underscores, as per the RFCs for domain name
construction (I forget which).

If you have a problem, set one or more of:

helo_allow_chars = _
helo_accept_junk_hosts = some.host.name:some.ip.add.ress

All of which are well documented.

Graeme

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