In this recipe, we'll learn how to monitor three common mail services for a nominated host: SMTP, POP, and IMAP. We'll also see how to use the same structure to include additional checks for secure, encrypted versions of each of these services: SMTPS, POPS, and IMAPS.
For simplicity, we'll assume in this recipe that all three of these services are running on the same host, but the procedure will generalize easily for the common case where there are designated servers for one or more of the previously mentioned functions.
You should have a Nagios Core 4.0 or newer server with at least one host configured already. We'll use the example of
troy.example.net, a host defined in its own file. You should also understand the basics of how hosts and services relate, which is covered in the recipes in Chapter 1, Understanding Hosts, Services, and Contacts.
Checking the connectivity for the required services on the target server is also a good idea to ensure that the...