Email And DNS

So you want to run your own email server, do you? If you have a static TCP/IP address, it's a great idea. I've been running my own copy of Argosoft Pro for over a year now and I'm very satisfied with the results. This gives me complete and utter control over sending and receiving messages, checking for spam and controlling spam. No ISP or other entity (such as Yahoo or Hotmail) is getting in the way with their restrictions and "features".

If you run your own email server, you must have (a) a static TCP/IP address (although I've heard rumors of ways to accomplish a static-like functionality with dynamic connections) and (b) some way to modify your domain's DNS entries.

So here's how it works from A to Z.

You get an "always-on" connection from your ISP (cable, DSL, T1 or something similar). Ensure the service includes at least one static TCP/IP address (you only need one address no matter how many computers you have).
Make sure you've got appropriate security in front of your system (a firewall).
Purchase your domain (unless you already have it) from your registrar.
To control your DNS entry for the domain, you can either (a) run your own DNS server (which is what I do and it's a great way to get control of things), (b) allow your ISP to control your DNS and ask (beg) them to make changes, or (c) use one of the free or paid DNS server services that are available (such as granitecanyon.com)
Include at least one MX record in your DNS entry (RFC 1912 requires two MX entries for redundancy). You will also need to include an A record matching the MX entry. Don't use CNAME's as documented in RFC 974, RFC 1034, RFC 1912, and RFC 2821. Also, the MX is to be a host name and not a TCP/IP address.
Use the tool at dnsreport.com to test your DNS record.

An example of the entries in your DNS is shown below. Note that only those entries related to email are shown.

mail A 123.126.0.1 mail2 A 123.126.0.2 @ MX 10 mail.rloweweb.com. @ MX 20 mail2.rloweweb.com.

This example says:

There is an email server named "mail.rloweweb.com" at the address 123.126.0.1 and it has a high priority (10).
There is another email server named "mail2.rloweweb.com" at the address 123.126.0.2 and it has a lower priority (meaning it is a secondary or backup email server to be used if the first one is down or unavailable).

According to RFC 822, RFC 1123, and RFC 2821 you should be sure to define the following email accounts:

postmaster - a general account for sending messages related to email.
abuse - used for spam-related messages (you can submit your abuse address to abuse.net).
null (no username at all) - used for general messages about the domain
It's also a good idea to define hostmaster for messages related to the domain name.

The lack of these accounts will not break anything, but having them follows standards. For example, allowing people to send to "abuse" may alert you to email abuse on your server and prevent your server from being blacklisted.