mail-abuse.org??, `"550 dial-up site refused"??,
,`127.0.0.$={OneTwoThree}.??)
Here, the $={OneTwoThree} class restricts a matchto any 127.0.0. address that ends in
a 1, 2, or 3. Other operators you might find useful are $+ (matchone or more), and
$@ (match zero tokens).
Note that beginning with V8.14, the second argument may be a literal discard or
quarantine:
FEATURE(enhdnsbl,`dialups.mail-abuse.org??, `discard??) ?†? V8.14 and later
FEATURE(enhdnsbl,`dialups.mail-abuse.org??, `quarantine??) ?†? V8.14 and later
Here, discard causes the rejected message to be silently accepted and discarded,
whereas the quarantine causes the rejected message to be accepted and quarantined.
This is the Title of the Book, eMatter Edition
Copyright ?© 2007 O??™Reilly & Associates, Inc. All rights reserved.
7.3 Check Headers with Rule Sets | 265
7.3 Check Headers with Rule Sets
Beginning withV8.10, sendmail provides the ability to screen selected headers with
rule sets. This is described in detail in ?§25.5 on page 1130. In this section, we show
two more techniques for using header checks to reject spam messages:
??? Reject messages that have subjects which indicate that the message contains a
virus.
??? Reject messages that have an illegally formed Received: header.
7.3.1 Virus Screening by Subject
Many messages that contain viruses, worms, or Trojan horses have distinctive subject
lines, the text of which is usually reported in the news.
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