[afnog] sendmail problem

[Stephane Bortzmeyer]

On Tue, Nov 07, 2006 at 03:42:25PM +0200,
 Alex Gondwe <agondwe at malswitch.com> wrote 
 a message of 12 lines which said:

> I have a mail server running sendmail. When the Internet connection
> or DNS fails the server fails to receive mail from the network.

It seems reasonable that no network means no email :-)

Unless you mean, "when the Internet connection or DNS fails the server
fails to receive mail EVEN from the LOCAL network." Is that so?

If so, your MTA probably tries to resolve the IP address of the sender
into a name and cannot reach in-addr.arpa nameservers. (Checking the
log file of sendmail - always the first thing to do - will allow you
to be sure.)

Check that the DNS resolver of the MTA can always resolve local IP
addresses, even without access to the Internet. For instance, if your
local addresses are 192.0.2.0/24, check that 2.0.192.in-addr.arpa is
directly reachable from this resolver (either because it is
authoritative for it or because it knows a forwarder which is).