The previously created items all required the Zabbix agent daemon to be installed, running, and able to make a connection in either direction. But what if you can't or don't want to install the agent on a remote host, and only need to monitor simple things? This is where simple checks can help you. These checks do not require any specialized agent running on the remote end, and only rely on basic network protocols such as ICMP and TCP to query monitored hosts.
Let's create a very basic check now. Open Configuration | Hosts, click on Items next to Another Host and click on Create Item. Fill in the values as follows:
Description: Enter SMTP server status
Type: Select Simple check
Key: Click the Select button. The Type dropdown at the upper-right corner should already say Simple check. If it doesn't, change it to that. In the key list, click on the smtp<,port> key, then edit it, deleting everything between the angle brackets, and the brackets themselves
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