You should definitely normalize e-mails before hashing or doing any comparison on the back end. Especially if you've had a stage during account creation where y

You should definitely normalize e-mails before hashing or doing any comparison on the back end. Especially if you've had a stage during account creation where you verified delivery of that normalized address. When you take in an address later you normalize the input and compare it to your stored value (that itself was normalized before storage).