In article <[EMAIL PROTECTED]> you write:
>Hello all.
>We have a client containing an underscore in the email address domain
>name. Our email server rejects it because of it's violation of the RFC
>standard. This individuals claim is that he doesn't have problems
>anywhere else and if this is going to be a problem he's "going to take
>his business elsewhere"!
>
>I understand it's a violation of the standard, but does it pose a
>security hole to the email server to allow this sort of mail?
>
>Thanks
>
RFC 952 and RFC 1123 describe what is currently legal
in hostnames.
Underscore is NOT a legal character in a hostname.
Before anyone says that domain names allow underscore which
they do.
RFC 1034 Section 3.3
For hosts, the mapping depends on the existing syntax for host names
which is a subset of the usual text representation for domain names,
together with RR formats for describing host addresses, etc. Because we
need a reliable inverse mapping from address to host name, a special
mapping for addresses into the IN-ADDR.ARPA domain is also defined.
Mail domains follow the same rules as for hostnames. RFC
821 and its replacement RFC 2821 havn't extended the syntax
to include underscores.
Mark
