September 2004
Intermediate to advanced
192 pages
10h 12m
English
Content preview from sendmail 8.13 CompanionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 9. DNS and sendmail
DNS stands for Domain Name System. A domain is any logical or physical collection of related hosts or sites, such as example.gov or www.example.gov.
What’s New with V8.13
The
dnsblfeature (7.2.1[3ed]) no longer uses thehostdatabase-map type to look up addresses. Instead, it uses thednsdatabase-map type (Section 9.1.1 [V8.13]).The
DNSBL_MAP_OPTmcmacro (Section 9.1.1 [V8.13]) has been added so that you may tune the database-map flags used with thednsblfeature.The
check_relayrule set (7.1.1[3ed]) is now called with the value of${client_name}macro (21.9.20[3ed]), allowing it to deal with bogus DNS entries (Section 9.1.2 [V8.13]).
Feature dnsbl Uses dns Database-Map
The dnsbl feature (7.2.1[3ed]) is used
to
enable the blocking of email
from open relay sites, dial-up sites, or known spamming sites. It
does so by invoking the RBL technique, which is discussed in
7.2[3ed].
Prior to V8.13, the dnsbl feature employed the
host database-map type
(23.7.9[3ed]) to look up addresses.
Beginning with V8.13, this feature now uses the
dns database-map type
(23.7.6[3ed]).
The default declaration for the dns database-map
for this feature looks like this:
Kdnsbl dns -R A -T<TMP>
If you wish to change the type of the lookup, you may redefine the
dns -R A part of the expression:
define(`DNSBL_MAP´, `dns -R TXT´) FEATURE(dnsbl, ...)
Here, the DNSBL_MAP redefines the
lookup
so that it performs TXT record lookups instead of
A record lookups. Note that
DNSBL_MAP must be defined ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.