The primary function of this check is to log in to 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.

LAST TESTED ON CHECKMK 2.3.0P1

Table of Contents

Step-by-step guide

Setup → Services → HTTP, TCP, EMail, ... → Check Email → Add Rule

Service description

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

Mail Receiving

You can select if you want to check your IMAP or POP3 login. It would be best to have your login credentials for your Email Mailbox.

Screenshot of New rule named Check Email. Imap Server enabled and set to imap.provider.com. TCP port enabled and set to 993.

Forward emails as events to Event Console
- Forwarding Method
  
  You can select if you want to send the events to the Event Console or a remote syslog host. If you want to send the events to the local EC, we recommend using the spooling mechanism.
  
  The check will store all collected events in one file in ~/var/mkeventd/spool using the spooling mechanism.
```
OMD[mysite]:~$ ll ~/var/mkeventd/spool/
total 3600
-rw-rw---- 1 mysite mysite 79124 Dec 7 15:36 mysite_407343_1607351778
-rw-rw---- 1 mysite mysite 79124 Dec 7 15:37 mysite_408329_1607351841
```

- Only process mails with matching subject

Use this option to not process all messages found in the inbox but only 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 official user guide.
.

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

Screenshot of Email header information

.

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

Screenshot of Regex examples

.

For advanced debugging:
.

Copy the plugin to the local path.

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

.

Add a print for the subject

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

.

Run the script manually

OMD[mysite]:~/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=user@provider.com' '--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

.

- Events: Syslog facility

Use this syslog facility for all created events.

- Events: Hostname

Use this hostname for all created events instead of the mail server's name.

- Limit the length of the mail body.

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

- Cleanup messages

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

Screenshot of Forward mails as events to Event console enabled. Forward method set to send events to local event console.

Debugging

Event Console Log

In the log of the Event Console, you can see the processing messages from the spool file:

~/var/log/mkeventd.log

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 helpful to run the check manually. Therefore, you need to open the service site of the Email service and search for 'Service check command'. Now you can use the command for executing the check manually.

Screenshot of Example of messages being set to the Event Console.

Screenshot of Example of a service command check

~/lib/nagios/plugins

OMD[mysite]:~/lib/nagios/plugins$ ./check_mail --pwstore=6@11@strato '--protocol=IMAP' '--server=imap.provider.de' '--ssl' '--port=993' '--username=user@provider.com' '--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

.

For a detailed log, you can use --debug at the end of the command:

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

.
For more information, you can use --help

OMD[mysite]:~$ ~/lib/nagios/plugins/check_mail --help

.

One alternative:

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

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

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

The Event would look like this:

Screenshot of Example event

Related articles

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Configuring Check Email (check_mail)
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How-to execute active checks manually
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Configuring Check Email Delivery (check_mail_loop)
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Configuring Informix

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