They send emails to IT. The classic example of a thing you can get through FOIA is large-scale dumps of emails from Exchange Servers, which is also not something a Clerk can do themselves, but which IT staff can immediately retrieve.
Leave the "Clerk" bit of this out and just imagine you're requesting straight from the IT department. What you can do: get anything not otherwise exempt that they know how to retrieve (it usually helps to provide example commands in the requests). What you cannot do: ask them to go look around and see what they have. That's research. Research is your job, not theirs, under Illinois FOIA.