This one time, at band camp, David P James said:
I've been trying to setup my Debian Woody network server as a mail
server as well.
At present I can send email to an account on that server from *within*
the lan using the server's internet domain name (davidium.dyndns.org) in
the email address, but not from outside (the connection times out,
according to the Failed Mail Delivery messages I get 4 hours later).
This may be iptables or it may be exim; I'm not sure. The email was sent
using exim on my own Debian box within the lan; specifing an external
smtp server results in a failed delivery however.
I'm using the ipmasq package that comes with Debian Woody, and I can at
present access other server functions from the outside such as http and
ftp, so I'm leaning towards a problem in exim.conf but as I said I'm
really not sure as I can't see anything amongst the exim.conf options
that should account for this.
As you have noted, there are quite a few variables. Rule out iptables
and tcpwrappers first - from an address outside the LAN, telnet
your.host.ip 25 - if the connection times out, it's probably iptables,
if it's refused, it's either iptables or tcpwrappers. If you connect
and get the exim greeting banner, then you know that the problem is your
exim.conf.