OT Sendmail configuration question

[Mark Campbell]

Is this what you're looking for?

During an SMTP conversation, a client introduces itself to a server
using the HELO or EHLO command. The standard does not specify what
should be said here, and many Windows clients in fact use a "bogus"
name: for instance, the domain name of the destination server.
Nevertheless, it may sometimes be useful to check the argument to
HELO/EHLO, as many SPAM programs use bogus arguments in a consistent
manner.

In a very helpful e-mail, a sendmail maintainer explained to me how this
could be done. The trick is to use delayed macro expansion with the $s
macro. As the sendmail manual explains, $s is a transient macro: at
startup, when sendmail reads its configuration file, it contains the
name of the host on which sendmail runs, but during an SMTP
conversation, it expands into the hostname supplied by the remote client
as the argument to HELO/EHLO. By writing $&s, it is possible to delay
the expansion of this macro, so it is expanded only when it is needed;
e.g., during Local_check_rcpt.

Consequently, my sendmail.mc file contains a local rule set similar to
the following (note that Local_check_rcpt, if exists, is automatically
called by sendmail at the appropriate stage of processing the envelope):

SLocal_check_rcpt
R$*                     $: $&s
Rbogus.domain           $#error $: 550 Spam Forbidden\ ($&s)
R$*                     $@ OK


REF: http://www.vttoth.com/heloehlo.htm

Mark

Mark Campbell
--
IT Convergence OS Administrator <mcampbell at itconvergence.com>


-----Original Message-----
From: MailScanner mailing list [mailto:MAILSCANNER at JISCMAIL.AC.UK] On
Behalf Of Jim Dickenson
Sent: Friday, February 11, 2005 4:48 PM
To: MAILSCANNER at JISCMAIL.AC.UK
Subject: OT Sendmail configuration question

Some time ago there was talk on this list about using a relatively new
option in sendmail. As I recall there is some option that allows one to
delay the response to a helo or ehlo line. The theory was that spammers
could not afford to wait when sending messages and they would not wait
for
the delay time.

Can someone remind me what the command was.

I tried to search the archive but not knowing exactly what I am
searching
for I did not find the past messages.

Thanks,
--
Jim Dickenson
mailto:dickenson at cfmc.com

CfMC
http://www.cfmc.com/

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