How do I search my Users for those without an email address?

The easiest way to search for user records that are missing an email address is to select the Manage Employees tab or the Managed Students tab (under Profiles) and then do an Advanced Search for [Last Name = *] AND [Email != * ].  This search string looks at all users (since you entered an asterisk for Last Name is searchs every record), and where the Email field DOES NOT equal "something".  In otherwords, if there is an entry in the email field, it skips that record.  If the user's email field is empty/blank/null - then it is displayed because there is nothing in the field.