Help Needed: My RHEL5 box suddenly stopped accepting e-mails

[Mun]

Hi Richard,

On Sat, May 7, 2011 at 1:50 PM, lists-redhat <
replies-lists-b3z1-redhat at listmail.innovate.net> wrote:

> if you're telnetting specifically to port 25, the smtp port (not
> generically to the machine, which will get you to port 23) and
> you're getting "connection lost" or "connection timed out", then you
> most likely have some type of a firewall issue.
>

Yes, for the experiment I was telnetting specifically to port 25.
Your assessment of the issue does appear to have merit: Note that when I
sent
an email from my gmail account to my workstation, gmail eventually sent me a
warning
stating that "The recipient server did not accept our requests to connect."
  Which
seems to reinforce your theory.


> from the machine itself, try telnetting to its port 25 *by ipnumber*
> (not name). make certain that you see that it's not trying to
> connect to 127.0.0.1 (which will probably happen if you try by
> name). if you get a connect, then it's likely an off-host
> firewall/routing issue.
>

I got a connection to sendmail.


>
> then, try telnetting to "127.0.0.1 25" -- you should get sendmail
> connect.
>

I got a connection to sendmail.


> if the telnetting to port 25 by the machine's ipnumber gets a hang
> then you likely have an on-host firewall issue. iptables is the most
> likely machine-specific firewall. you can look in /etc/sysconfig to
> see if you have an iptables setup. if so, turn iptables off and try
> telnetting in to port 25 (by ipnumber and from off-host) and see
> what you get.
>
> if the issue appears to be an off-host firewall issue, then you need
> to step back and see what's going on from the outside.
>

It would seem that I am here, right?


>
> [honestly, if you did nothing to your machine setup, i'd bet on some
> external/network change to be causing your issue.]
>

I'm a little nervous that the updates that were installed did something to
cause this
side affect--but by reading their descriptions, that shouldn't of been the
case.  Furthermore,
since I downgraded the respective patches I should be back to a working
system.

Thus, I am in agreement that it _does_ seem to be something external to my
machine.
Although, my IT dept does not agree; so I may be out of luck.


>
> [by the way, you don't need to reboot the machine to restart
> sendmail, or other service starts/stops (rebooting to restart/fix
> things is the windows approach to life, and not generally necessary,
> or recommended, in the unix world.)]
>

Agreed.  I did the reboots in response to downgrading packages.  Strictly
speaking,
the downgrades did not require reboots.  But because the downgrade had no
affect on my problem,
I thought I'd reboot--just in case.  Plus, I was desperate.

Kind regards,

-- 
Mun



>
>  - Richard
>
>
> ------------ Original Message ------------
> > Date: Saturday, May 07, 2011 01:09:55 PM -0700
> > From: Mun <mjelists at gmail.com>
> > To: redhat-list at redhat.com
> > Subject: Re: Help Needed: My RHEL5 box suddenly stopped accepting
> e-mails
> >
> > Hi Richard,
> >
> >
> > On Sat, May 7, 2011 at 3:38 AM, lists-redhat <
> > replies-lists-b3z1-redhat at listmail.innovate.net> wrote:
> >
> >> in your .cf, what do you have as an active (not commented out)
> >> option the under:
> >>
> >>  # SMTP daemon options
> >>
> >> tag?
> >>
> >> is it:
> >>
> >>  O DaemonPortOptions=Port=smtp,Addr=127.0.0.1, Name=MTA
> >>
> >> or something more along the lines of one of the following:
> >>
> >>  O DaemonPortOptions=Name=IPv4, Family=inet
> >>
> >>  O DaemonPortOptions=Name=MTA
> >>
> >
> > I have the choice immediately above in my sendmail.cf:
> > DaemonPortOptions=Name=MTA
> >
> >
> >>
> >> The first, with the 127.0.0.1, is the default for RHEL and will
> >> only accept localhost mail. The other two are forms will allow it
> >> to accept mail from off localhost.
> >>
> >> If that looks ok, try telnetting to port 25 on this machine from
> >> off-host - e.g., from the exchange server. Do you get a
> >> "connection refused" response or a "hang". If "connection
> >> refused", then it's most likely the sendmail daemon doing the
> >> blocking. If you get a "hang", then it's likely a firewall of
> >> some nature, e.g., iptables.
> >>
> >
> > I get "connection lost" or "Connection timed out"; depending on
> > the computer I use to run telnet.
> > The "connection lost" is what my Windows XP box returned; and the
> > "Connection timed out" is what
> > another Linux box returned.
> >
> >
> >> Have you looked at your machine's logs (maillog, messages, secure
> >> being the most obvious) they may give some hints.
> >>
> >
> > Yes.  I have looked at those, as has the company's IT dept.  But
> > there were no messages that
> > would help with this issue.
> >
> >
> >>
> >> Have you restarted sendmail?
> >>
> >
> > Yes.  I've also rebooted a coupled of times; nothing seems to help.
> >
> > It's just so weird that with no obvious changes made (except for
> > the updates applied and then
> > downgraded that I mentioned in my initial message) that my box
> > would just all of the sudden
> > stop accepting email.
> >
> > Thanks very much for the reply.  I greatly appreciate the ideas.
> >
> > Regards,
> >
> > --
> > Mun
> >
> >
> >
> >>
> >>       - Richard
> >>
> >>
> >>
> >> ------------ Original Message ------------
> >> > Date: Friday, May 06, 2011 04:48:34 PM -0700
> >> > From: Mun.Johl at emulex.com
> >> > Subject: RE: Help Needed: My RHEL5 box suddenly stopped
> >> > accepting
> >> e-mails
> >> >
> >> > Hi Richard,
> >> >
> >> > Thanks for your reply.
> >> >
> >> > I had saved off /etc/mail when we first got email working
> >> > properly on my system (a couple of years ago) and I compared
> >> > the current sendmail.cf to the "known good" copy.  The only
> >> > difference I see is that IT has uncommented the following line:
> >> >
> >> > O Timeout.ident=0
> >> >
> >> > With respect to sendmail.mc, the version currently used by the
> >> > system had the following lines commented out:
> >> >
> >> > MASQUERADE_AS(`mydomain.com')dnl
> >> > FEATURE(masquerade_envelope)dnl
> >> > MASQUERADE_DOMAIN(localhost)dnl
> >> > MASQUERADE_DOMAIN(localhost.localdomain)dnl
> >> >
> >> > I'm not too experienced with sendmail, but it doesn't appear to
> >> > me as if the changes above would result in the problem I am
> >> > having; does it?
> >> >
> >> > Regards,
> >>
> >> ------------ End Original Message ------------
> >>
> >>
>
> ------------ End Original Message ------------
>
>
>