how "not in" query linq?

i have twin collections have ability email both collections. i need list equipment initial list where email does exist second list. sql i only "not in", nonetheless i know homogeneous linq. done?

so distant i have join, like...

var matches = item1 list1
join item2 list2 item1.email equals item2.email
select new { email = list1.email };

but i can't join given i need inadequacy join fail. i need proceed controlling contains exists i believe. i only have found an instance yet.