Hashing is completely irreversible. You cannot hash an email address and then unhash it. At most you can brute-force guess the email until the hash matches, but this is basically impossible.

Hashing the email address would break one of the main reasons to use an email address - the ability to send emails to users.

Encrypting email addresses is fine, but you wouldnt compare the encrypted data, you'd just decrypt and compare the original email address.