[CentOS] Not receiving mail

[Les Mikesell]

On 10/18/2010 3:38 PM, Dotan Cohen wrote:
> On Mon, Oct 18, 2010 at 22:34, Steve Clark<sclark at netwolves.com>  wrote:
>> Hmm... I am not having any problem connecting from the U.S.
>>
>> ping 178.63.65.136
>> PING 178.63.65.136 (178.63.65.136) 56(84) bytes of data.
>> 64 bytes from 178.63.65.136: icmp_seq=1 ttl=49 time=140 ms
>> 64 bytes from 178.63.65.136: icmp_seq=2 ttl=49 time=142 ms
>> 64 bytes from 178.63.65.136: icmp_seq=3 ttl=49 time=138 ms
>>
>> telnet 178.63.65.136 25
>> Trying 178.63.65.136...
>> Connected to 178.63.65.136.
>> Escape character is '^]'.
>> ^]
>> telnet>  close
>> Connection closed.
>>
>
> Exactly the problem! It pings fine (so I know that connections can be
> established over the physical wires) and on the IP address telnet
> answers. However, telnet to port 25 (smtp) with the domain name fails.
> Why could that be?

No the example above shows a telnet to port 25 connecting - which I can 
reproduce too - but there is no 220 response as there should be from a 
mailserver.  Either the process is hung or configured to black/graylist 
unknown connections, or something other than mailserver is listening on 
port 25.

Telnet is going to go to an A record, so you have to look up the MX 
record first, then telnet to the target.

-- 
   Les Mikesell
     lesmikesell at gmail.com