Section 4.1.2 RFC2821: "To promote interoperability and consistent with long-standing guidance about conservative use of the DNS in naming and applications (e.g., see section 2.3.1 of the base DNS document, RFC1035std13 [22]), characters outside the set of alphas, digits, and hyphen MUST NOT appear in domain name labels for SMTP clients or servers. In particular, the underscore character is not permitted. SMTP servers that receive a command in which invalid character codes have been employed, and for which there are no other reasons for rejection, MUST reject that command with a 501 response."
William -----Original Message----- From: Toni, Randy [mailto:[EMAIL PROTECTED]] Sent: Monday, March 25, 2002 2:49 PM To: MS-Exchange Admin Issues Subject: OT - RFC 2822 and the underscore from hell... I'm trying to read through RFC 2822 to determine if an underscore is a valid part of a hostname for a mail server. We allow it on our SMTP proxy (any host that connects to us with a "_" in the hostname is not a problem). But there is one server out there that is killing our outbound messages because a demo relay that I set up out in our DMZ has an underscore in the hostname. This hostname shows up in the header and they whack it (kind of rude but maybe they're right to do so...) This is easy to fix but I'd like to know if I'm the one breaking the rules here. Seems to me that the structure of a mail server hostname can contain an underscore (or a period, etc.) as part of the "atom" or "dot-atom" component in the "local-part" of the "addr-spec" (which meshes with the filbert-flange and the grapple-grommet). This stuff makes me dizzy (dizzier?). I'm looking at http://www.zvon.org/tmRFC/RFC2822/Output/chapter3.html#addr-spec Is there anyone who can unscramble this doc for me and help with the sanity check? The more I read it the more my brain resembles a dot-atom (but in spite of that, BTW thanks to whoever it was who posted this site for RFC's) many thanks - as usual randy. List Charter and FAQ at: http://www.sunbelt-software.com/exchange_list_charter.htm List Charter and FAQ at: http://www.sunbelt-software.com/exchange_list_charter.htm
