FQDN and Message-IDs
From 40tude Dialog Wiki
The following is blatantly ripped from a nice explanantion I found here and here. While they deal with leafnode and InterMapper configuration, they still contain excellent explanations of FQDNs and Message-ID generation.
What is a FQDN?
This is an acronym for a "Fully-Qualified Domain Name." Within an organization, it's convenient to refer to a computer by the first part of its name, knowing that "everyone" will know that the remainder is the same as the other computers in the organization. Thus, you may speak of "sneezy" and "dopey", knowing that they're really two computers at "seven-dwarves.org".
But computers need the fully-spelled out name (the FQDN), such as "sneezy.seven-dwarves.org." or "dopey.seven-dwarves.org." to identify a computer.
What is a Message-ID?
Every message (mail or news) has a unique identifier in its header, the Message-ID. It may not be visible in your software unless you choose display all headers or display raw or display source.
The Message-ID looks roughly like an E-Mail address, <email@example.com>: it has a local and a domain part, separated by an @ sign, only that the local part of the Message-ID is different for different pieces of mail or news, while the local part of the mail address is constant. The domain part is usually the name of the host that generated the Message-ID: your computer's name when you are sending mail or posting news.
Whenever a news server is offered a new news article for redistribution, it looks at the Message-ID to determine if it already has the article, to avoid double work, and to avoid that news articles run in circles.
Therefore, each message sent, mail or news, must have a unique Message-ID. If the Message-ID is not unique, because you use the same host name as somebody else, and you and the other person write an article at the same time, either article will be discarded by the server.
How can we garantee the uniqueness of our Message-ID? This is where our FQDN comes into play. We use our personal FQDN for the domain part of our message ID. This has the advantage that we can score on replies to our posts because our FQDN will be in the reference of any posts that follow-up to ours. The generation of the local part of the Message-ID is Dialog's job.
How can I get a FQDN?
First off, you might already have one. If you own your own domain, then you need look no further. You can use it, perhaps in combination with a subdomain(iE news.myfqdn.com) to generate your message-ids.
There are also at least two places where you can obtain a FQDN for free.
Sign up for a low cost news account with the fine people at news.individual.net Not only can you get a free FQDN, you also get access to an excellent news server. Be sure to read their FAQ for the information on the FQDN.