Ian
▸ quoted from Ian Diddams
On Thu, 28 Oct 2021 at 23:08, Ian Diddams via Xymon <xymon at xymon.com> wrote:
we ahve a client configured thus
10.108.249.162 colt # ssh ntp MAINTNC:linux smtp
This smtp c
heck has been green for ever - literally. It has suddenly alerted
▸ quoted from Ian Diddams
overnight and is remaining so
Service smtp on colt is not OK : Service listening but unavailable
(connect timeout)
Seconds: 0.001814000
"listening" means it's accepting TCP connections.
I can telnet from the xymon server on port 25 fine.
"connect timeout" means xymonnet was waiting for something that didn't come
in time. I wonder if you have an "expect" string in the [smtp] section of
protocols.cfg, causing xymonnet to wait for a string containing "220" but
that never arrives.
▸ quoted from Ian Diddams
postfix services on colt are working seemingly correctly (eg i can send a
mail successfully from a client that uses colt as a smtp server)
So Im now trying to find out what it is that this smtp check atually does
in order to find out why it now thinks it cant do it.
The error suggests indeed its a timeout issue - but the telnet test
connects immeditaely (no obvious lag anyway)
thoughts/
ian
Maybe check your Postfix logs to see if something is happening there. Have
you upgraded/reconfigured Postfix recently? In some configurations, Postfix
has been known to reject "pipelining" which is sending multiple commands
(eg "mail" and then "quit") without waiting for a response after each
command. When this happens, Postfix rejects the command, but doesn't send a
"220" nor does it close the connection. Or it might be as simple as your
Xymon server being removed from Postfix's allowed senders lists.
Here's the [smtp] section from the standard protocols.cfg:
[smtp]
send "mail\r\nquit\r\n"
expect "220"
options banner
port 25
Compare with yours.
You could do a packet capture to see what the dialog looks like, and
compare it to the send/expect in protocols.cfg. You could try simulating
the "send" string from protocols.cfg (after telnetting to port 25) and see
if you get a 220 response. You could comment out the expect string in
protocols.cfg and see if it starts working. You could take a look at (and
perhaps even share here) the banner displayed in the smtp check status
page, as that might give a clue as to what's not right.
I seem to recall a discussion about SMTP pipelining on this list, only a
few weeks ago. Perhaps re-read that discussion to see if there are any
nuggets of wisdom that could help.
Cheers
Jeremy