Re: [Exim] Mail Reject Because Of Helo .xxxx

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Szerző: Kjetil Torgrim Homme
Dátum:  
Címzett: Dominik Ruf
CC: exim users
Tárgy: Re: [Exim] Mail Reject Because Of Helo .xxxx
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.