Re: [Exim] HELO syntax checking in Exim 4

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Autor: Philip Hazel
Fecha:  
A: Nigel Metheringham
Cc: Exim Users Mailing List
Asunto: Re: [Exim] HELO syntax checking in Exim 4
On 15 Mar 2002, Nigel Metheringham wrote:

> Is there some special handling of underscore elsewhere? The reason I
> ask is I remember in the dim and distant past we needed to front end the
> DNS handling functions with code to deal with underscores because some
> particularly broken resolver implementations died horribly when passed
> an underscore and querying a name server which rejected them.


I think you are thinking of dns_check_names_pattern. The default value
for this accepts only letters, digits, and hyphens in domain components.
(So underscore is "just another illegal character" in this regard.)

Underscores are, of course, NOT illegal in DNS domain names. However,
they ARE illegal in host names and email domain names. This causes a lot
of confusion.

Philip

--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.