Right but in this case you would essentially have to use every salt from every user to hash the submitted email and say "aha user 123,456 has a salt and hashed

Right but in this case you would essentially have to use every salt from every user to hash the submitted email and say "aha user 123,456 has a salt and hashed email which matches the submitted email of foo@example.com" which is why I suggested method 2. I am user "Arnor" and my email is "foo@example.com". Ok, your salt is #@$%@#$%DGDFfdgdawer. If your hashing algorithm is appropriately "expensive" the scan all user salts would not work.