In order to use exMon, you need to have an exMon user account. This account defines preferences, permissions, groups, email definition and is audited with all actions of the user.
You can connect this account to you existing external system. This can be beneficial if you need to automatically create all users that are defined as a responsible person in a query. For example, if you are testing your employee time registration system.
This can be done easily with External Systems and Users which can be found under General -> Configuration -> External Users.
exMon comes with 3 external systems, Active Directory, Email and Expectus User Id. Adding other systems can be done under "Edit External Systems".
In this picture we see a few external users being mapped to exMon users. Notice here that the external user id does not need to be a numeric value, but can be whichever unique value your underlying system uses to differentiate between users.
Another thing to notice is the Expectus User Id mapping, which can seem strange to some. This, however, makes it easier for developers to map exMon user ids to the user behind them (their name or email address).