[105840] in North American Network Operators' Group
Re: REJECT-ON-SMTP-DATA (Re: Mail Server best practices - was:
daemon@ATHENA.MIT.EDU (=?ISO-8859-1?Q?Jean-Fran=E7ois_Mez)
Sat Jul 5 04:53:05 2008
Date: Sat, 05 Jul 2008 04:52:43 -0400
From: =?ISO-8859-1?Q?Jean-Fran=E7ois_Mezei?= <jfmezei@vaxination.ca>
To: nanog@nanog.org
In-Reply-To: <2008070502062564justin@justinshore.com>
Errors-To: nanog-bounces@nanog.org
one note about whether to filter at receiving SMTP server or later.
The receiving SMTP server is the one that has the conversation with the
sender.
Rejecting mail from servers having an un-backtranslatable IP is best
done right away by the receiving server right after the HELO command by
issuing error message about the IP being unbacktranslatable. Reduces the
load.
later on (for instance at the client level), you need to parse the
RFC822 text header and there are some bits that are missing, notably the
RCPT TO: commands. This is especially true when the "TO" in the 822
header is faked.
Blocking messages as early as possible also greatly reduces the load on
your system, disk storage requirements etc.
