Steps to reproduce :
1. Go to Global Administration -> Mail -> Advanced
2. Choose to obfuscate email addresses
3. Save the changes
4. Go to Global Administration -> User Directory
5. Notice that Email is one of the fields listed to be displayed in the table above
6. Filter in the User Directory table by email

Expected result : only the users matching the given email would be displayed.
Actual result : the results are not filtered by the given email.