Email issues, relay failure

[Jon Radel]

On 2/25/12 10:26 AM, Bender, Chris wrote:

>
> On telnet w IP it says unable to connect.
...
> Its weird that the delivery on A says deferred connection timed out but on tcpdump I see the port 25


If you can't establish a TCP connection from A to your relay server on 
port 25, I'd expect all of the above.  If you can't establish a TCP 
connection to port 25 at all from A, I'd stop focusing on the details of 
the e-mail server on the relay machine (as they're likely to be beside 
the point) and start focusing on what is blocking the traffic from A. 
Have you audited all the firewalls involved?  To be really focused, if 
you see traffic (both ways) at the relay server when A tries to talk to 
port 25, but A is convinced that no TCP connection is established, 
either you're stomping on things at the relay server (do your attempts 
to telnet to port 25 fail immediately or just sit there for a good long 
time and then fail?), the reply packets from relay to A are getting 
mis-routed, or A is ignoring the packets coming in from the relay.  Can 
you ping from the relay to A?

There's a distinct difference between failure to establish a TCP 
connection (look to the network stuff) and the e-mail server giving you 
an error response rejecting your attempt to transfer mail or just 
quietly loosing the mail (look to the e-mail servers).

-- 
--Jon Radel
jon at radel.com