I think it would be a good idea to offload that logic elsewhere. One thing to think about if/when you do that is that there is logic that strips out whitespace and fixes capitalization from submitted email addresses, and it would be important to ensure that the validation still takes place at the same step in the sequence. I had trouble simulating some of the regex attacks that the Rails 4 regex rules are meant to protect against because of the string cleanup that Clearance performs outside of validation.