status failed when contact smtp server

[Anace BYAOUI]

Hi All,

I have a problem with the smtp server check, there seems to be a fake problem in reporting the smtp server contact status, I tried with a script to contact the smtp server and it appears that it is reachable every time monit reports this error:

in “log”:

[CEST Apr 16 16:40:22] error : 'smtp2.domain.com' failed protocol test [SMTP] at [smtp2.domain.com]:25 [TCP/IP] -- Error receiving data from the mailserver -- Resource temporarily unavailable

‌

in “monit status”:

Remote Host 'smtp2.domain.com'
status Connection failed
monitoring status Monitored
monitoring mode active
on reboot start
port response time FAILED to [smtp2.domain.com]:25 type TCP/IP protocol SMTP
data collected Thu, 16 Apr 2020 17:44:44

my config :

in file '/etc/monit.d/host'

check host smtp2.domain.com with address smtp2.domain.com
group SMTP
if failed port 25 and protocol smtp for 20 cycles then alert

in file ‘/etc/monitrc’

set mailserver smtp2.domain.com

‌

could you please help me ?

thank you in advance

Anace

[Tildeslash]

Hi,

‌

please can you send us a network trace of the communication between monit and your smtp server? You can use for example wireshark or tcpdump to capture the data.

best regards

[Anace BYAOUI]

hi,
I have attached the trace.
please let’s me know when you have received it, then i can delete it from the issue

‌

best regards

Anace

[Tildeslash]

got it, you can delete the attachment

[Anace BYAOUI]

thank you

[Tildeslash]

it is quite strange … the capture contains 3 attempts to connect to the SMTP server, where the client did TCP reset immediately after it received a valid response from the server (most probably monit’s SMTP checks)

‌

Then there is one successful SMTP transaction between monit and the server when monit sent the alert message via the same server … which worked fine.

‌

I have tried to reproduce the problem, adding an SMTP check for the server IP which is visible in the trace … works fine:

'xxx' succeeded testing protocol [SMTP] at [xxx]:25 [TCP/IP] [response time 309.765 ms]

'xxx' connection succeeded to [xxx]:25 [TCP/IP]

‌

It seems that the problem is on lower layer … maybe some firewall killing the connection or incompatible TCP/IP settings.

‌

I’m not sure if we can help you in this case, it is probably a network problem, not monit bug.

[Anace BYAOUI]

Thank you for the feedback.

could you please send me the config you put to get this log:

'xxx' succeeded testing protocol [SMTP] at [xxx]:25 [TCP/IP] [response time 309.765 ms]
'xxx' connection succeeded to [xxx]:25 [TCP/IP]

‌

[Tildeslash]

‌

set daemon 5

set httpd port 2812 allow localhost

check host shared-proxy-01.zimbra.id with address 93.62.133.224
        group SMTP
        if failed port 25 and protocol smtp for 20 cycles then alert

‌

and executing it via “monit -vIc <path to configuration file>”

[Anace BYAOUI]

it seems that it remains stable for some time at the first check and then reports that it has failed:

the status in the first check :

Remote Host ' smtp2.domain.com'
status OK
monitoring status Monitored
monitoring mode active
on reboot start
port response time 3.716 s to smtp2.domain.com:25 type TCP/IP protocol SMTP
data collected Fri, 17 Apr 2020 14:51:15

after :

Remote Host 'smtp2.domain.com:25
status OK
monitoring status Monitored
monitoring mode active
on reboot start
port response time FAILED to [smtp2.domain.com:25 ]:25 type TCP/IP protocol SMTP
data collected Fri, 17 Apr 2020 14:52:50

‌

I can't explain this behavior.

‌

[Tildeslash]

it really seems as intermittent network issues

[Tildeslash]

not bug