This is not trivial task, actualy you need to overwrite this devise method inside your model:
def send_confirmation_instructions
if reconfirmation_required?
self.confirmation_token = nil if reconfirmation_required?
@reconfirmation_required = false
ensure_confirmation_token!
opts = pending_reconfirmation? ? { :to => unconfirmed_email } : { }
send_devise_notification(:reconfirmation_instructions, opts)
else
super
end
end
Then you need to extend Devise::Mailer
to add method reconfirmation_instructions
And finally you need to create view app/views/devise/mailer/reconfirmation_instructions.html.erb