Test SMTPS from Command Line

Just like the testing of SMTP using Telnet, you can also perform the same steps if the target server is using TLS, however because telnet won’t do the job here, you can use OpenSSL instead. Here’s a simple example:

check_http and SNI Hostnames

You may find you need to perform a check where the FQDN you are monitoring doesn’t correspond to the IP address and some form of virtual server (or host headers) are in use. Now normally using a command like: Should just work however in certain instances depending on the configuration of the web server you’ll … Read more

OSI Model (7 Layers)

The OSI Model (Open Systems Interconnection) model is a set of rules and requirements to model and conceptualise the communication between two (network) systems. Yes, its theory, but in computing and networking it can be useful to use as a basic guide when troubleshooting. It helps you to rule-in or rule-out where a problem might … Read more