On Sat, 2004-05-01 at 23:49 +0200, Dominik Ruf wrote:
> 2) Yes, this provider is also doing something which breaks the
> RFCs, because rejecting based on HELO is a MUST NOT. However,
> more and more admins are doing some kind of HELO checks these
> days to fight against spam/worms.
technically, "HELO .example.com" can not be recognized as a valid
command according to the grammar, so the client has not issued a HELO at
all. RFC 2821 section 4.1.1.1 says: "[...] a client MUST issue HELO or
EHLO before starting a mail transaction."
you are probably thinking of section 4.1.4, which is about much stricter
checking:
An SMTP server MAY verify that the domain name parameter in the EHLO
command actually corresponds to the IP address of the client.
However, the server MUST NOT refuse to accept a message for this
reason if the verification fails: the information about verification
failure is for logging and tracing only.
--
Kjetil T.
