[CentOS] Sendmail problem - baffled

Tue May 15 21:18:22 UTC 2012
John Hinton <webmaster at ew3d.com>

On 5/15/2012 4:57 PM, Bowie Bailey wrote:
> On 5/15/2012 4:48 PM, Jussi Hirvi wrote:
>> On 15.5.2012 23.22, Alexander Dalloz wrote:
>>> It is technically impossible that the telnet to target port 25 succeeds
>>> from the same system on which the Sendmail gets a connection refused,
>>> unless Sendmail is configured to use a non-standard target port.
>> That is why I am baffled. :-/
>> I could use a way to see what port sendmail is actually using to make
>> the contact. My assumption is that when the log entry (see my orig post)
>> says "mailer=esmtp,", it implies port 25 - but then it really does not
>> make sense that the connection is refused.
>> On the primary mail server (which I try in vain to contact) I see
>> *nothing* about the failed connections in the maillog, even though I
>> raised log_level to 19.
> You could use wireshark to monitor the network traffic and determine
> exactly what happens when sendmail tries to make the connection.
A couple of things to check. I don't know if these servers are in the 
same location or not but it is possible if not, that your provider 
blocks port 25. Here are two configs to check.

dnl # The following causes sendmail to only listen on the IPv4 loopback 
dnl # and not on any other network devices. Remove the loopback
dnl # address restriction to accept email from the internet or intranet.
dnl #
DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl

If this is not done on the primary, it will not listen to anything but 
itself.... so the backup wouldn't be able to contact it.

dnl #
dnl # The following causes sendmail to additionally listen to port 587 for
dnl # mail from MUAs that authenticate. Roaming users who can't reach their
dnl # preferred sendmail daemon due to port 25 being blocked or 
redirected find
dnl # this useful.
dnl #
DAEMON_OPTIONS(`Port=submission, Name=MSA, M=Ea')dnl

and this if it is possible that port 25 is blocked.

Sorry if this has already been discussed. I stepped in late on the 

John Hinton
877-777-1407 ext 502
Comprehensive Online Solutions