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Re: domain name definition in RFC2821

2007-03-23 08:28:39

John C Klensin wrote:

4) One-label names permitted, no trailing dot ever.

Advantages:
- obviously compatible with (2)822
- no arbitrary TLD exclusion

Issues with "name completion" can be fixed in the MON,
probably at the MSA as specified in 4409 chapter 8.8.

Disadvantage:
- For an MX "HELO oemcomputer" and "HELO ws" would be
  both sytactically valid.

How about adding a note like this:
  
| Of course servers are free to reject clients based on
| any properties of the client <Domain>, and this might
| include to reject all top level <Domain>s.  However
| rejecting top-level <Domain>s SHOULD NOT be done with
| 50x replies.

Plus a pointer to this chapter in the "differences from
2821" appendix G (at the moment the change log, but you
probably transform it into a persistent appendix later.) 
 
In input to a submission server, the client must agree
with the server on some method to distinguish between
an incomplete domain name and a TLD.

Maybe that could be done in the security considerations:

| Where outgoing servers transform local names to FQDNs
| (see RFC 4409 ch. 8.8) allowing host names matching
| TLD names can be unwise, and likewise TLD operators
| are encouraged to use FQDNs with more than one label
| when using SMTP over the Internet.

Frank


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