I configured nagios to monitor CPU, memory, disk, POP, SMTP and IMAP in my Zimbra server. All options are working fine except for SMTP service which always shows "socket timeout after 10 seconds" for the past few days but during this time i am able to send and receive emails.
Yesterday in some of the systems where mail is configured in MS outlook shows error while i do send and receive (attached screenshot). When i do send and receive again after some time it works fine. This issue does not happen for all the accounts and also doesn't occur all the time.
Can someone guide me on how to proceed with this issue.