Sparkpost throws 500 when email is invalid, catching error doesn't work

[gbrl]

I followed the instructions in the README, setting up action_mailer.rb file to catch SparkPostRails::DeliveryException but it doesn't seem to work.

The issue is that if you use sparkpost with devise, and a user tries to register with an email that doesn't have any MX records... (example: user@gmails.com) sparkpost throws a DeliveryException, and my app crashes. Am I doing something wrong? Here's my action_mailer.rb file

ActionMailer::DeliveryJob.rescue_from(SparkPostRails::DeliveryException) do |exception|
  redirect_to '/logout', alert: "Please use a valid email address."
  # do something special with the error
end