Skip to Content
DNS on Windows Server 2003, 3rd Edition
book

DNS on Windows Server 2003, 3rd Edition

by Cricket Liu, Matt Larson, Robbie Allen
December 2003
Intermediate to advanced
416 pages
13h 50m
English
O'Reilly Media, Inc.
Content preview from DNS on Windows Server 2003, 3rd Edition

MX Records

DNS uses a single type of resource record to implement enhanced mail routing, the MX record. Originally, the MX record’s function was split between two records, the MD (mail destination) and MF (mail forwarder) records. MD specified the final destination to which a message addressed to a given domain name should be delivered. MF specified a host that would forward mail on to the eventual destination, should that destination be unreachable.

Early experience with DNS on the Internet showed that separating the functions didn’t work very well. A mailer needed both the MD and MF records attached to a domain name (if both existed) to decide where to send mail—one or the other alone wouldn’t do. But an explicit lookup of one type or another (either MD or MF) would cause a name server to cache just that record type. So mailers either had to do two queries, one for MD and one for MF records, or they could no longer accept cached answers. This meant that the overhead of running mail was higher than that of running other services, which was eventually deemed unacceptable.

The two records were integrated into a single record type, MX, to solve this problem. Now a mailer just needed all the MX records for a particular domain name destination to make a mail-routing decision. Using cached MX records was fine, as long as the TTLs matched.

MX records specify a mail exchanger for a domain name: a host that will either process or forward mail for the domain name (through a firewall, ...

Become 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,
and much more.

Read now

Unlock full access

More than 5,000 organizations count on O’Reilly

AirBnbBlueOriginElectronic ArtsHomeDepotNasdaqRakutenTata Consultancy Services

QuotationMarkO’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.
Head of Cybersecurity
QuotationMarkI 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.
Field Engineer
QuotationMarkI’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.
Data Platform Tech Lead
QuotationMarkI'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.
Mark W.
Embedded Software Engineer

You might also like

Windows Server 2016: Unleashed

Windows Server 2016: Unleashed

Rand Morimoto, Jeffrey Shapiro, Guy Yardeni, Omar Droubi, Michael Noel, Andrew Abbate, Chris Amaris
Mastering VMware vSphere 6.7 - Second Edition

Mastering VMware vSphere 6.7 - Second Edition

Martin Gavanda, Andrea Mauro, Paolo Valsecchi, Karel Novak
Pro DNS and BIND 10

Pro DNS and BIND 10

Ron Aitchison
Exam Ref MD-100: Windows 10, First Edition

Exam Ref MD-100: Windows 10, First Edition

Andrew Bettany, Andrew Warren

Publisher Resources

ISBN: 0596005628Errata Page