RubyOnRails E-Mail Whitelisting for Mailer

email_interceptor.rb

class EmailInterceptor
  
  # just an example to allow only *@zauberware.com emails
  REGEX_WHITELIST = /.*@zauberware\.com/

  def self.delivering_email(message)
    if !in_whitelist?(message.to.first)
      message.perform_deliveries = false
    end
  end

  def self.in_whitelist?(email)
    email.match(REGEX_WHITELIST) ? true : false
  end
end

# usage:
# create a file under app/initializers/
# file should include
# ActionMailer::Base.register_interceptor(EmailInterceptor)