Check Email (check_mail)

The basic function of this check is to log in into an IMAP or POP3 mailbox to monitor whether or not the login is possible. An extended feature is, that the check can fetch all (or just some) from the mailbox and forward them as events to the Event Console.

Step-by-step guide

1. WATO - CONFIGURATION → Host & Service Parameters → Active checks → Check Email

2. CHECK EMAIL

   1. Service description

      1. Here you can type in a service description. Please make sure that this is unique per host and does not collide with other services.

   2. Mail Receiving

      1. Here you can select if you want to check your IMAP or POP3 login. You need your login credentials for your E-Mail Mailbox.

         

   3. Forward mails as events to Event Console
      

      1. Forwarding Method

         1. Here you can select if you want to send the events either to the EC or to a remote syslog host. If you want to send the events to the local EC, we would recommend using the spooling mechanism.
            By using the spooling mechanism, the check will store all collected eventsin one file in ~/var/mkeventd/spool.
            

            OMD[nagnis_master]:~$ ll ~/var/mkeventd/spool/
            
            total 3600
            
            -rw-rw---- 1 nagnis_master nagnis_master 79124 Dec 7 15:36 localhost_407343_1607351778
            
            -rw-rw---- 1 nagnis_master nagnis_master 79124 Dec 7 15:37 localhost_408329_1607351841
            
            

            
            

      2. Only process mails with matching subject

         1. Use this option to not process all messages found in the inbox, but only the those whose subject matches the given regular expression. The text entered here is handled as a regular expression pattern. The pattern is matched from the beginning. Add a tailing $ to change it to a whole text match. The match is performed case sensitive. Read more about regular expression matching in Checkmk in our user official guide.
            
            

            1. You need to be aware that a subject field could contain line breaks. This is depending on your mail client and mail gateway. To find out how many line breaks you have, you could check the raw email

               

               1. Now you can use regex platforms like regex101.com to create a regex

                  

               2. For advanced debuging

                  1. Copy the plugin to the local path

                     OMD[mysite]:~/lib/nagios/plugins$ cp check_mail ~/local/lib/nagios/plugins/

                  2. Add a print for the subject

                     104     for index, msg in sorted(mails.items()):
                     105         subject = msg.get('Subject', 'None')
                     106         print(subject)

                  3. Run the script manually

                     OMD[jph2]:~/lib/nagios/plugins$ ./check_mail --pwstore=6@17@password_1 '--fetch-protocol=IMAP' '--fetch-server=imap.strato.de' '--fetch-tls' '--fetch-port=993' '--fetch-username=mail@anastasios-thomaidis.de' '--fetch-password=*************' '--connect-timeout=10' '--forward-ec' '--match-subject=.*Incident.*\n.*assigned' 
                     =?utf-8?Q?Incident_INC000000XXXX_has_bee?=
                      =?utf-8?Q?n_assigned_to_your_group_'XXXX=
                      =?utf-8?Q?XXXXX'_=XXXXX:_Comuni?=
                      =?utf-8?Q?XXXXX_-_Priority:_Low?=
                     =?utf-8?Q?Incident_INC000000XXXX_has_bee?=
                      =?utf-8?Q?n_assigned_to_your_group_'XXXX=
                      =?utf-8?Q?XXXXX'_=XXXXX:_Comuni?=
                      =?utf-8?Q?XXXXX_-_Priority:_Low?=
                     Forwarded 2 messages to event console | messages=2
                     
                     

      3. Events: Syslog facility

         1. Use this syslog facility for all created events
            
            

      4. Events: Hostname

         1. Use this hostname for all created events instead of the name of the mailserver
            
            

      5. Limit length of mail body

         1. When forwarding mails from the mailbox to the event console, the body of the mail is limited to the given number of characters.
            
            

      6. Cleanup messages

         1. The handled messages (see subject matching) can be cleaned up by either deleting them or moving them to a subfolder. By default nothing is cleaned up.
            

            

Debugging

EC Log

In the log of the EC you can see the processing messages from the spool file:

2020-12-07 12:51:18,078 [20] [cmk.mkeventd.EventServer] Processing message '<21>Dec 7 12:51:17 localhost Checkmk EC: Checkmk EC|Email to EC of Checkmk!'

2020-12-07 12:51:18,079 [20] [cmk.mkeventd.EventServer] Parsed message:

application: Checkmk EC

core_host:

facility: 2

host: localhost

host_in_downtime: False

ipaddress:

pid: 0

priority: 5

text: Checkmk EC|Email to EC of Checkmk!

time: 1607341877.0

Execute active Check manually

For debugging reasons it could be useful to run the check manually. Therefore, you need to open the service site of the E-Mail service and search for 'Service check command'. Now you can use the command for executing the check manually.

OMD[nagnis_master]:~/lib/nagios/plugins$ ./check_mail --pwstore=6@11@strato '--protocol=IMAP' '--server=imap.provider.de' '--ssl' '--port=993' '--username=mail@provider.de' '--password=*************' '--forward-ec' '--forward-method=spool:' '--match-subject=Checkmk EC' '--forward-facility=2' '--forward-host=localhost' '--cleanup=delete'
OK - Forwarded 0 messages to event console | messages=0

OMD[nagnis_master]:~$ ~/lib/nagios/plugins/check_mail --pwstore=6@11@strato '--protocol=IMAP' '--server=imap.provider.de' '--ssl' '--port=993' '--username=mail@provider.de' '--password=*************' '--forward-ec' '--forward-method=spool:' '--match-subject=Checkmk EC' '--forward-facility=2' '--forward-host=localhost' '--cleanup=delete' --debug

 ~/lib/nagios/plugins/check_mail -h

OMD[dashboard]:~$ lq "GET services\nColumns:host_name description check_command_expanded\nFilter: host_name = localhost\nFilter: description = Email"
localhost;Email;check_mk_active-mail!--pwstore=6@11@cmkmail '--protocol=IMAP' '--server=imap.strato.de' '--ssl' '--port=993' '--username=cmk@anastasios-thomaidis.de' '--password=****************' '--forward-ec' '--forward-method=spool:' '--forward-facility=2' '--forward-host=localhost'

OMD[dashboard]:~$ cd ~/lib/nagios/plugins/

OMD[dashboard]:~/lib/nagios/plugins$ ./check_mail --pwstore=6@11@cmkmail '--protocol=IMAP' '--server=imap.strato.de' '--ssl' '--port=993' '--username=cmk@anastasios-thomaidis.de' '--password=****************' '--forward-ec' '--forward-method=spool:' '--forward-facility=2' '--forward-host=localhost' --debug

The Event would look like this:

Related articles