Capture email address

I have a form that users fill out and when they click to submit the form, the details are then emailed to a specific address.
We currently have the form capturing the username of the person that filled out the form by how they are logged onto the network.
What I would like to know is, instead of capturing their username, could I get their email address instead or both.
The code is ran with ASP and currently it’s listed as “strUser = UCase(Request.Servervariables(“LOGON_USER”))”.
I’m not the one who generated the code to capture this, so i’m not sure if getting the user’s email address is possible or not, but if anyone knows how to do so under ASP I would like to know.
Thank you
MT