*   Add `assert_enqueued_email_with` test helper.

        assert_enqueued_email_with ContactMailer, :welcome do
          ContactMailer.welcome.deliver_later
        end

    *Mikkel Malmberg*

*   Allow Action Mailer classes to configure their delivery job.

        class MyMailer < ApplicationMailer
          self.delivery_job = MyCustomDeliveryJob

          ...
        end

    *Matthew Mongeau*


Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actionmailer/CHANGELOG.md) for previous changes.