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Old 06-09-2008, 04:48 PM
Ray Leventhal
 
Default sendmail not sending after reboot UPDATE

lists-centos wrote:

are you configured for spamassassin or clamav as milters on the
server (in the sendmail.cf) and either/both of these didn't start up
on the reboot? sendmail will still accept mail with sa/clamav not
running, but it takes a bit longer.
there's also the possibility of an inverse-map lookup on the
ipnumbers of the inbound client machines. if the server is trying to
do the lookups but is having trouble reaching the appropriate
in-addr.arpa server you'll get long hangs.

- Rick


Hi Rick,

no milters are configured...this is a really small intranet with
absolutely no connectivity to the outside world.


I'm baffled. Regarding your mention of a dns issue...it may be, but i'm
still baffled as this was all working before the weekend. I rebooted
the box on Sunday and am in this <pun intended> bind today


Thanks for your input...much appreciated.
-R
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Old 06-09-2008, 04:49 PM
Ray Leventhal
 
Default sendmail not sending after reboot UPDATE

<snip>


where does the server point to for its dns? if it's (supposed to be)
running a nameserver (e.g., you're pointing to 127.0.0.1) but the dns
server isn't running you'll get a timeout. if you have a second
nameserver configured in /etc/resolv.conf you'll likely ultimately
get a response, but only after you time out on the first.

by the way, you may want to look at the server's "client" sendmail
queue ("mailq -Ac"). the remote clients dump to the regular queue
(/var/spool/mqueue), but localhost mail goes into the clientmqueue
(/var/spool/clientmqueue). if mail is hanging there it might give
hints that are easier to debug than are remote connections. [you may
also want to try originating mail from localhost and see what
happens.]



- Rick




The server points to another server on the network for dns, which is
running and accepting queries on 53, as expected. resolv.conf points to
the correct nameserver IP.


I'll check the client queue..hadn't thought of that.
Thanks,
-Ray

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Old 06-09-2008, 05:08 PM
Stephen Harris
 
Default sendmail not sending after reboot UPDATE

On Mon, Jun 09, 2008 at 11:34:11AM -0400, Ray Leventhal wrote:
> This now seems like a timeout issue. Increasing client-side timeout to
> > 180 seconds gets mail going just fine.
>
> Any ideas on what might be happening since a reboot to cause this change
> in MTA behaviour would be greatly appreciated.

DNS. It's always DNS :-)

(more accurately, host and IP address resolution).

How long is it taking your server to resolve the IP address into a
name? To resolve names into IP addresses? To resolve destination MX
records?

--

rgds
Stephen
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Old 06-09-2008, 08:46 PM
Ray Leventhal
 
Default sendmail not sending after reboot UPDATE

<snip>


DNS. It's always DNS :-)

(more accurately, host and IP address resolution).

How long is it taking your server to resolve the IP address into a
name? To resolve names into IP addresses? To resolve destination MX
records?



Hi Stephen,

While I agree, I'm still a bit stumped. Nothing changed other than a
reboot on Sunday afternoon. I do have Friday's rsync snapshot and running
diff against the sendmail files (cf/mc) as well as hosts, resolv.conf,
etc...all showed no differences.


Thanks,
-Ray
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Old 06-10-2008, 02:43 AM
Stephen Harris
 
Default sendmail not sending after reboot UPDATE

On Mon, Jun 09, 2008 at 04:46:47PM -0400, Ray Leventhal wrote:
> >DNS. It's always DNS :-)

> While I agree, I'm still a bit stumped. Nothing changed other than a
> reboot on Sunday afternoon. I do have Friday's rsync snapshot and running
> diff against the sendmail files (cf/mc) as well as hosts, resolv.conf,
> etc...all showed no differences.

Ah, there's where the reboot magic comes in. When you start sendmail it
picks up the resolving configuration when you started. If nsswitch.conf
or resolv.conf changed _afterwards_ then sendmail may not have noticed....
until you reboot!

Many core configuration files (eg tzdata) has this issue; the relevant
libraries load the configuration at start time.

Now I say "may" in the above because if you have nscd then it's very possible
to change configurations without restarting daemons if you nudge nscd.

But, for safety, changing name resolving configurations is better followed
by daemon restarts or rebooting... just for safety.

--

rgds
Stephen
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