It appears the current filter for Email only permits an "Is Defined" operator (simply checking that email exists). However a quick way to find people who work for XYZ company is to search fo XYZ.com as a domain, which doesn't appear possible from the filters. It's acknowledged that one can use either the main search or the filter search for XYZ.com domain, but being able to use "Contains" on the email field would be useful. Thanks!