On Thu, Apr 13, 2000 at 09:45:08AM +0530, Dr. S.K. Singh wrote:
>
> I am facing a strange problem in SUSE Linux 6.3. My server
> "cirg.up.nic.in" sending mails to outside domain and within the domain
> but not receiving the mails from outside domain. Mails sent from
> outside are neither received nor they are bouncing back.
>
> I have checked IP address which are proper. I am able to browse
> the server with name "cirg.up.nic.in" from outside domain so DNS and
> IP are OK. Any suggestions please!
You can see if sendmail (or some other process) has bound to port 25, by
using netstat:
% netstat -naf inet
You should see (among other things) something like:
Active Internet connections (including servers)
Proto Recv-Q Send-Q Local Address Foreign Address (state)
tcp4 0 0 *.25 *.* LISTEN
tcp4 0 0 10.0.0.1.53 *.* LISTEN
The *.25 local port is the one used by sendmail. If you start sendmail
from your boot scripts, and you see messages written in your logs like:
Apr 10 03:12:33 hades sendmail[14319]: NOQUEUE: SYSERR(root):
opendaemonsocket: cannot bind: Address already in use
then some other process has bound a socket to port 25, and sendmail can
not receive incoming requests for mail. The most common culprit for
such evil things is inetd, so look in your /etc/inetd.conf and see if
some service listed there opens your smtp port (tcp/25).
Other things that might have you blocked out from your sendmail are
tcpwrappers, so you want to make sure that hosts.allow and hosts.deny
files in /etc do not block access to your sendmail.
If that is all fine, then you might want to look around for firewalls,
and other beasts that block incoming connections to your sendmail. This
is easy to find out, though. When I temporarily blocked my own sendmail
from me, with a firewall rule, a simple telnet to port 25 would give:
% telnet localhost 25
Trying 127.0.0.1...
telnet: connect to address 127.0.0.1: Permission denied
telnet: Unable to connect to remote host
--
Giorgos Keramidas, < keramida @ ceid . upatras . gr >
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