RE: [exim] reject-log question

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Author: David Brodbeck
Date:  
To: exim-users
Subject: RE: [exim] reject-log question
> -----Original Message-----
> From: Michael F. Sprague [mailto:mfs@sanellc.net]


> Steffen Heil <lists@???> wrote:
> > Hi
> >
> > > The underscore in the domain name. It isn't permitted.
> >
> > Are you sure?
> > Is it better to tell that client to change the name
> > OR is it better to allow it?
> >
> > Usually I like it more to keep on standards.
> > But I need to be sure, that this is indeed really not permitted.


I think the standard for hostnames is RFC-952. (Someone can correct me if
it's been obsoleted by something more recent.) It states:


1. A "name" (Net, Host, Gateway, or Domain name) is a text string up
to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus
sign (-), and period (.). Note that periods are only allowed when
they serve to delimit components of "domain style names". (See
RFC-921, "Domain Name System Implementation Schedule", for
background). No blank or space characters are permitted as part of a
name. No distinction is made between upper and lower case. The first
character must be an alpha character. The last character must not be
a minus sign or period. A host which serves as a GATEWAY should have
"-GATEWAY" or "-GW" as part of its name. Hosts which do not serve as
Internet gateways should not use "-GATEWAY" and "-GW" as part of
their names. A host which is a TAC should have "-TAC" as the last
part of its host name, if it is a DoD host. Single character names
or nicknames are not allowed.


Underscores are clearly not part of the spec.

> It's better to get the client to fix it, but since you're
> probably dealing with
> an MS client; good luck. You're better off allowing the
> underscore. :)


True. So many hosts have this wrong that I ended up just allowing it.