[Techtalk] kindergarten mail server question

[Kai MacTane]

At 2/21/02 08:47 AM , Carla Schroder wrote:
>Example: trusty Postfix server is all set up and configured at 
>carlas.domain.com, ready to start work moving mail over the Internet. Well 
>somewhere out there are DNS and MX thingies that have to be configured, 
>right? Assume I can log into wherever to do all this. (in this case, my 
>domain name registrar provides user DNS management.)

Just to deal with the worst-case first, I'll assume that you're going to be 
subdividing carlas.domain.com into various hosts on different IPs, such as:

     www.carlas.domain.com   10.1.2.3
    mail.carlas.domain.com   10.1.2.4
   other.carlas.domain.com   10.1.2.5

Since Web is a pretty standard service, your registrar-provided DNS should 
already have an entry in the carlas.domain.com domain, saying:

    www   10.1.2.3

You'll want to add one entry for each other host, such as:

    mail   10.1.2.4
   other   10.1.2.5

Then -- and here's the part you're probably really wondering about -- 
you'll also want to add at least one MX record. Preferably at least two. 
Suppose your friend has agreed to do secondary MXing for you at 
carlas.friend.com. Your MX entries should look like this:

    MX  10   mail.carlas.domain.com
    MX  20   carlas.friend.com

You can use any numbers you like for this, but your primary *must* have a 
lower number than your secondary (and any tertiaries). Most(?) people start 
at 10, then increment by 10, allowing some room for expansion and change. 
(I've seen some folks start at 10 and then jump to 100, or just start at 
100 and increment by hundreds. Those both work fine, too.)

When you're done, you should be able to do "telnet mail.carlas.domain.com 
25" from anywhere on the Net and see your mail server's (E)SMTP banner. 
(Then type "quit" to break the connection gracefully.)

(Of course, you may need to wait for the DNS to propagate.)

Most likely, you're working with the "special case" scenario, in which all 
your subhosts are on the same IP. No problem, this just means the IP 
addresses listed in the second part of each line will all be the same.

>I've been studying all kinds of docs, and I have a feeling there's a few 
>simple steps buried in the masses of verbiage somewhere. Thanks for any 
>links or help.

I think what you wanted was to know about the MX lines. If this explanation 
leaves you with other questions (or still with the same questions!) let me 
know, and I'll try to fill in any gaps.

                                                 --Kai MacTane
----------------------------------------------------------------------
"When the clouds pull apart/And the Moon changes phases,
  In the quiet, secret places/Are you there? Are you there?"
                                                 --Concrete Blonde,
                                                  "Darkening of the
                                                   Light"