searching within a mailbox in Discovery Accelerator

Hi. Thanks for the time.  I apologize for the noob questions.  I am just trying to get my head around Discovery Accelerator.

If I want to search for items within a single user's mailbox...how would I go about it?

This is what I have done so far:

-created a new case for that new user

-under search terms:

  i-To or from: user@domain.com

  ii-subject or content: investigation

however the it is searching the entire email vault.  Is there a way to only search through this user's mailbox and the contents he/she has.?

appreciate the feedback.