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A primer on messaging standards: NNTP, X.400 and LDAP

An introduction and explanation of a few messaging protocols relevant to the seasoned Exchange administrator's vocabulary: NNTP, X.400 and LDAP.

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In part one of this two-part series, I discussed the SMTP, POP and IMAP protocols and explained why they are important to Exchange administrators. In this article, I cover a few other protocols relevant to the seasoned Exchange administrator's vocabulary: NNTP, X.400 and LDAP.


Network News Transfer Protocol is one of the most underused messaging protocols. NNTP is used to communicate with newsgroups on the Internet. Newsgroups exist on a variety of subjects; some allow members to post content, while others are read-only.

Although there are loads of useful newsgroups available on the Internet, most administrators are reluctant to deploy newsgroup readers, because they can't track which newsgroups users are accessing or control the amount of bandwidth consumed by using them. Many administrators simply choose to block NNTP at the firewall level at the first thought of it.

Instead of blocking NNTP completely though, you do have the option of using Exchange as your NNTP client. You can configure Exchange Server to subscribe to specific newsgroups and make that content available to your users through a public folder. Your users wouldn't require direct access to the NNTP protocol. Outlook would communicate with Exchange as a MAPI client, and only your Exchange server itself would act as an NNTP client.


The X.400 protocol is a bit archaic, but it's important nonetheless. X.400 gives an Exchange organization a mechanism through which it can communicate with foreign e-mail systems. You're definitely less likely to run into it in these SMTP days we're in. Still, X.400 is still occasionally used to provide a direct communications path between an Exchange organization and a foreign mail system (or even another Exchange organization). (Take a look at this X.400 FAQ if you're intrigued.)

The X.400 protocol tends to look a bit strange to those who have never seen it before. Rather than using style e-mail addresses, X.400 addresses look more like "c=US;a=;p=comapny;o=Admin;s=Posey;g=Brien." This big, long e-mail address is not as cryptic as it might first appear. There is a method to the madness. Here is a breakdown of what the different letters mean:

C     Country
A     Administrative management domain 
      (This is often unused.)
P     Private management domain
      (In an Exchange environment, this is the Exchange organization name.)
O     The X.400 organization
      (In an Exchange organization, this is the administrative group name.)
S     User's last name
G     User's first name


Lightweight Directory Access Protocol, which is based on the X.500 standard, is the protocol that Exchange Server uses to communicate with Active Directory. To really understand what LDAP is and what it does, you need to understand the basic concept behind Active Directory as it relates to Exchange.

Active Directory contains information regarding every user account on the entire network (among other things). It treats each user account as an object. Each user object also has multiple attributes. An example of an attribute is the user's first name, last name, or e-mail address. All of this information exists within a huge, cryptic database on a domain controller (Active Directory). The challenge therefore becomes extracting information you need in a usable format.

That is LDAP's job. LDAP uses a relatively simple, string-based query to extract information from Active Directory. The nice part is that this all happens behind the scenes. A normal user will never have to manually perform an LDAP query, because Outlook is LDAP-enabled and knows how perform all the necessary queries on its own.

About the author: Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. Brien has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer he has written for Microsoft, TechTarget, CNET, ZDNet, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal Web site at

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