Re: [Exim] HELO syntax check

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Autor: David Woodhouse
Data:  
A: Tamas TEVESZ
CC: Chris Edwards, exim-users
Assumpte: Re: [Exim] HELO syntax check
ice@??? said:
>     The RFCs mandate that a server must not reject a message because
>     it doesn't like the HELO or EHLO command.


> "MUST NOT", that is. may i suppose you are out of luck here, as far as
> exim goes ;).


I don't see that in RFC2821.

I see (§4.1.4, para 5):
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.

... but that only seems to mean that you mustn't refuse to accept the mail
because the name provided doesn't match the DNS. It doesn't necessarily
mean that you must accept mail even if the EHLO isn't syntactically valid.

In fact, looking at the second paragraph of the same section:
A session that will contain mail transactions MUST first be
initialized by the use of the EHLO command. An SMTP server SHOULD
accept commands for non-mail transactions (e.g., VRFY or EXPN)
without this initialization.

Doesn't look like you MUST even accept non-mail commands without a valid
EHLO, let alone mail commands.

--
dwmw2