Julian Mehnle wrote:
Strict 2821 implementations could reject "HELO ws" and "HELO ws."
as SMTP syntax errors.
I don't think this is correct. A strict interpretation of RFC 2821
requires only the "EHLO" command -- not the "HELO" command -- to
have an FQDN. (This is obviously due to RFC 821 _not_ requiring an
FQDN with "HELO", and due to many legacy implementations not giving
Please join the IETF SMTP list, the 2821-to-DS effort was restarted.
For the issue at hand, 2821 claims to obsolete 821, and a strict 2821
implementation would by definition do whatever 2821 says. There are
some cases where 2821 explicitly says "look into 821 for details".
| (However, for compatibility with older conforming implementations,
| SMTP clients and servers MUST support the original HELO mechanisms
| as a fallback.) Unless the different characteristics of HELO must
| be identified for interoperability purposes, this document discusses
| only EHLO.
The details are explained in section 126.96.36.199 (EHLO or HELO), and the
specified syntax is:
| ehlo = "EHLO" SP Domain CRLF
| helo = "HELO" SP Domain CRLF
So the syntax is in essence identical, with the (in)famous "one dot":
| Domain = (sub-domain 1*("." sub-domain)) / address-literal
So why do you think that a strict-2821 server "should" (?) not reject
HELO ws / HELO ws. but would reject EHLO ws / EHLO ws. ? Somewhere
501 is explicitly mentioned as possible reaction after EHLO:
| If the EHLO command is not acceptable to the SMTP server, 501, 500,
| or 502 failure replies MUST be returned as appropriate.
Now I'm cheating and jump to 821, where the corresponding text is:
| If the HELO command argument is not acceptable a 501 failure reply
| must be returned and the receiver-SMTP must stay in the same state.
Clearly 501 is allowed after both HELO and EHLO, but this might be
about an EHLO or HELO in a state where it makes no sense.
John has posted "HELO" as open issue for 2821bis, so far no replies.
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