Based on the custom field i'm assuming that you're getting the email from the current post that is being created by the form. In this case you should be able to do this.
Problem:
The user would like to have a search, with term fields, in a taxonomy view.
Solution:
Custom search is not possible for taxonomy views and user views. It is only possible for post views. We have an existing feature request for custom taxonomy searches and I have added your voice to the request.
However, I believe that a workaround can be implemented using custom code. At the end, taxonomy views are just a wrapper around a WP_Term_Query instance. And we do offer a hook to modify the arguments that would be passed to it:
