Add postfix monitoring setup

.gitignore

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+.DS_Store

README.md

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 # zabbix
 
+## Setting Up Monitoring for a Postfix Service
+
+### On the Mail Server
+
+1. Edit the Zabbix agent configuration file:
+`vim /etc/zabbix/zabbix_agent2.d/postfix.conf`
+
+2. Add the following line:
+`UserParameter=postfix.running,script /tmp/postfix-script-zabbix.log -qc 'sudo postfix status' | grep -c 'PID'`
+
+3. Ensure your Zabbix agent is configured for active checks by checking these parameters in your `/etc/zabbix/zabbix_agent2.conf`:
+```
+ServerActive=your_zabbix_server_ip
+HostnameItem=system.hostname
+```
+
+4. Restart the Zabbix agent:
+`systemctl restart zabbix-agent2`
+
+5. Check the status of the Zabbix agent:
+`systemctl status zabbix-agent2`
+
+The mail server's Zabbix agent will now collect the Postfix status using a script command and report that data back to the Zabbix server. The Zabbix server must then be configured to processes this information and handle alerting.
+
+### In the Zabbix web interface:
+
+1. Create a new item for your host
+`Data collection -> Hosts -> Items (column next to the desired host) -> Create item (at top right)`
+
+2. Set the following parameters:
+- Name: `Monitor postfix service`
+- Type: `Zabbix agent (active)`
+- Key: `postfix.running`
+- Type of information: `Text`
+- Description (optional): `Monitor postfix service.`
+
+![sample-config-item](sample-config/postfix.running-zabbix-item.png)
+
+3.  Click "Add" to save the item
+
+4. Create a trigger based on the return value
+`Data collection -> Hosts -> Triggers (column next to the desired host) -> Create trigger (at top right)`
+
+5. Set the following parameters (Replace instances of `mail_server_hostname` with your actual host name in Zabbix):
+- Name: `Postfix service is not running on {HOST.NAME}`
+- Severity: `High`
+- Problem expression: `last(/mail_server_hostname/postfix.running)=0`
+- OK event generation: `Recovery expression`
+- Recovery expression: `last(/mail_server_hostname/postfix.running)>0`
+- PROBLEM event generation mode: `Single`
+- OK event closes: `All problems`
+- Description (optional): `Postfix has stopped running.`
+
+![sample-config-trigger](sample-config/postfix.running-zabbix-trigger.png)
+
+6. Click "Add" to save the trigger
+
+This trigger will fire when the Postfix check returns 0 (not running) and will automatically resolve when the check returns a value greater than 0 (running).