Verify failed SQL Server connections to instances on a given server and email them I am trying to monitor the SQL Server instances on standalone server / cluster server. I would like to setup something from commandline to check for connectivity to each SQL Server instance on the server. Wherever it fails to connect to an instance I would like to have an email (we have smtp server setup) sent to our DBA team. 

Each server is having more than 5 instances and we are unable to track them without customer complaining about connectivity, hence trying to be proactive.

Can we try something like osql or sqlcmd?
You can use server audit specification to track failed logins.
use ssis and a script task to read audit file and email it if needed.