Re: [exim] hostname and HELO/EHLO response

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Author: Edgar Lovecraft
Date:  
To: Exim User's Mailing List
Subject: Re: [exim] hostname and HELO/EHLO response
Stuart Gall wrote:
> >
> > Then you did not quite read it 100% correctly. RFCs cannot dictate
> > site policies.
>
> Yes but read on .............
>
> The sender-SMTP MUST ensure that the <domain> parameter in a
> HELO command is a valid principal host domain name for the
> client host. As a result, the receiver-SMTP will not have
> to perform MX resolution on this name in order to validate
> the HELO parameter.
>
> The HELO receiver MAY verify that the HELO parameter really
> corresponds to the IP address of the sender. However, the
> receiver MUST NOT refuse to accept a message, even if
> sender's HELO command fails verification.
>


And look at it again, the <domain> parameter is not a just a hostname,
i.e. 'EHLO hostname' is not a valid command, but 'EHLO domain.com'
'EHLO hostname.domain.com', and 'EHLO [1.2.3.4]' are valid SMTP
HELO/EHLO commands, there is no reason at all that any SMTP server
should accept an improperly formatted command, and using 'EHLO hostname'
or 'EHLO 1.2.3.4' is not valid command syntax.

> >
> > Nobody is forced to do that either -- and many sites will allow SMTP
> > clients to lie about their hostname, or to use otherwise bogus or
> > invalid hostnames.
>
> Nobody is forced to do anything. I am just saying that the
> administrator has configured their server
> to tell people to read the RFC when they themselves are violating it.


They are following the RFC because the error message that was given said
they would not accept a HELO/EHLO command were only the 'hostname' and
not the FQDN or 'domain' was given. All that was presented to thier
server was 'ehlo hostname', they should not accept that any more than
they should accept a improperly formed "MAIL FROM:" or "RCPT TO:"
command.

>
> I dont believe anyone except a spammer would deliberately forge the HELO
> but many sites have poorly configured servers
> when an important client has a badly configured server no one wants to
> hear from sysadmin that it is their fault :-(((


The original error message returned had NOTHING to do with forging the
EHLO hostname, they rejected the command because only a hostname was
presented.

Here is the original error as given by the original poster as found here:
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-
20041018/msg00146.html

<ERROR>
SMTP error from remote mailer after HELO mail:
host mail.sourceforge.net [66.35.250.206]: 550 Don't like your HELO/EHLO.
Hostname must contain a dot.
</ERROR>



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