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A good example of heavily broken SMTP client
I do not check HELO neither syntaxically nor for A RR now, just
because too many of our business correspondent's corporate mailhosts
use WinNT with broken HELO. In other case, this message could be
blocked easily without MAPS RSS assistance: either by non-reversed IP
or by strange HELO. And we can understand that the reasons of last
two misconfigurations (HELO and open relay) is exactly the same:
broken //root/dev/hands. Reverse IP is more complex problem, but
(seems) normally anybody may and can use provider's smarthost for
outbound mail until reverse zone delegation.
However, now I have realized that it is possible to implement formal
HELO check in Zmailer using regexps in smtpserver.conf. Actual HELO-
to-A-RR check and reverse DNS... seems, it requires new features.
Other idea: applying regexps to reverse DNS result can filter many
dialups which are not announced in MAPS DUL. *dialup*, *ppp*, etc.
------- Forwarded message follows -------
Date sent: Fri, 15 Jun 2001 00:12:43 +0400 (MSD)
From: MAILER-DAEMON@office.cpr.spb.ru (Mail Delivery System)
To: firstname.lastname@example.org (Postmaster)
Subject: Postfix SMTP server: errors from unknown[18.104.22.168]
Transcript of session follows.
Out: 220 office.cpr.spb.ru ESMTP Postfix
In: EHLO SamPost.SAMPOST
Out: 250-SIZE 3000000
Out: 250 8BITMIME
In: MAIL FROM:<*email@example.com> SIZE=2381
Out: 250 Ok
In: RCPT TO:<*firstname.lastname@example.org>
Out: 550 Service unavailable; [22.214.171.124] blocked using
Out: 221 Bye
No message was collected successfully.
------- End of forwarded message -------
Alexey A. Lobanov AL258-RIPE
Clinical Pharmacological Research Institute, Head IT dept.
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