The User Function apoc.data.domain will take a url or email address and try to determine the domain name. This can be useful to make easier correlations and equality tests between differently formatted email addresses, and between urls to the same domains but specifying different locations.

WITH 'foo@bar.com' AS email
RETURN apoc.data.domain(email) // will return 'bar.com'

WITH 'http://www.example.com/all-the-things' AS url
RETURN apoc.data.domain(url) // will return 'www.example.com'