For example, the following rule allows EXPN if the connecting host is the local
machine, and denies it otherwise.
Table 19-3. Characters that set/clear server features
On Off Description
a A Offer the AUTH SMTP extension.
b B Offer use of the SMTP VERB command (V8.13 and later).
c C C is the equivalent of AuthOptions=p; i.e., it doesn??™t permit mechanisms susceptible to simple passive
attack (e.g., PLAIN, LOGIN), unless a security layer is active.
d D Offer the DSN SMTP extension (V8.13 and later).
e E Offer the ETRN SMTP extension (V8.13 and later).
l L Require the client to authenticate with AUTH (V8.13 and later).
p P Offer the PIPELINING SMTP extension.
r R Request a certificate (V8.13 and later).
s S Offer the STARTTLS SMTP extension.
v V Verify a client certificate.
x X Offer use of the SMTP EXPN command (V8.13 and later).
This is the Title of the Book, eMatter Edition
Copyright ?© 2007 O??™Reilly & Associates, Inc. All rights reserved.
710 | Chapter 19: The S (Rule Sets) Configuration Command
LOCAL_SRV_FEATURES
R $* $: $&{client_addr}
R 127.0.0.1 $# e
R $* $# E
A special character, the t, is used to force a temporary failure:
LOCAL_SRV_FEATURES
R $* $: $&{client_addr}
R $- . $- . $- . $- $: $1.$2.$3
R 123.45.67 $# temp
Here, the connecting host??™s address is found in the $&{client_addr} macro. The second
rule strips off the host part of a class-C address.
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