network problems

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Author: Robert Ambrose
Date:  
Subject: network problems
Do you have the-arcanum.org listed in sendmail.cw/local-host-names (or
whatever the name de jour is)? The MX record for you internal DNS zone
should point to the system which will receive the email. Since the email
shouldn't be going outside your LAN, port blocking by Qwest should not be
an issue. Specifying an A record for the-arcanum.org is not necessary to
get email delivered to the-arcanum.org, the MX record does this.

A very useful technique for debugging how an email address will be
delivered to is to use the -bt option with sendmail:

sendmail -bt
3,0

Will show how sendmail thinks an email addressed to this recipient will
be delivered.

rna

On Wed, 21 Jan 2004, Nathan England wrote:

>
> I am trying to setup internal e-mail on my systems and I'm having weird
> problems. My firewall is 192.168.0.1, my e-mail (sendmail and ipop3d)
> are on 192.168.0.2, .2 is also my internal dns that all my machines use.
>
> My firewall is setup for eth0 being my vdsl connection, eth1 is my
> internal nic. All machines connect to the outside via iptables nat.
>
> Qwest blocks port 25, I think that's my problem, coming from the
> internal nat.
>
> when 192.168.0.5 sends an e-mail, it goes to .2 which resolves
> the-arcanum.org as internal 192.168.0.1, when I watch sendmail on .2, it
> says it is deferred and stops. It won't send it.
>
> I tried changing my dns to resolve the-arcanum.org to be .2 , but that
> didn't work, it came back saying that the message loops back to itself,
> MX problem. So I added MX records for the-arcanum.org to point to .2 but
> then sendmail just times out trying to send a message.
>
> Is this all because qwest is blocking 25 and I'm internally nat'ing, or
> something else? I didn't have this problem when I had normal dsl without
> any ports being blocked, but maybe I'm missing the problem.
>
> Can anyone shed some light on this for me?
>
> nathan
>
>