Allow mailers to configure their delivery job

Setting delivery_job on a mailer class will cause MessageDelivery to use
the specified job instead of ActionMailer::DeliveryJob:

    class MyMailer < ApplicationMailer
      self.delivery_job = MyCustomDeliveryJob

      ...
    end

1 files changed, 10 insertions, 0 deletions

diff --git a/actionmailer/CHANGELOG.md b/actionmailer/CHANGELOG.md
index e488d867de..83067dfd38 100644
--- a/actionmailer/CHANGELOG.md
+++ b/actionmailer/CHANGELOG.md
@@ -1 +1,11 @@
+* Allow ActionMailer 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.