How to get mail to local destinations delivered?

[Tim]

On Sun, 2007-11-11 at 14:28 +0000, Chris G wrote:
> What I *don't* quite understand is why sendmail thinks this is
> isbd.net and why I couldn't tell it what the system should really be
> called.  Everything else (apache, ssh, etc.) thinks it's called
> home.isbd.net. 

Have you set those other services up explicitly, or are they all
presuming something?

I recall that some services will check the current hostname, do a
reverse IP look up on that name, then do a forward name look up on that
IP, and go with the last result.

e.g. If your hosts file had:

  192.168.1.1 computer.example.com  computer

in it, and the computer hostname was set at "computer" (the hostname is
NOT "set" by the hosts file, that's done elsewhere), a service would
check the the IP for computer, get told 192.168.1.1, then it'd check
what hostname is associated with that IP, and go with the answer (which
will be the first name after the IP), and decide that it is
computer.example.com.

The same sort of thing applies for DNS, rather than the hosts file (the
first answer is it).

Things get can messy when something/somebody puts their hostname into
the local loopback line (the 127.0.0.1 one).

Mail server address working out can be a little surprising if you have
proper DNS records.  You may well have the computer set to be
home.example.com, but if the MX record for the example.com domain is set
to example.com, that's the mail server address.

-- 
(This computer runs FC7, my others run FC4, FC5 & FC6, in case that's
 important to the thread.)

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