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diff --git a/actionmailbox/lib/action_mailbox/base.rb b/actionmailbox/lib/action_mailbox/base.rb
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+++ b/actionmailbox/lib/action_mailbox/base.rb
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+# frozen_string_literal: true
+
+require "active_support/rescuable"
+
+require "action_mailbox/callbacks"
+require "action_mailbox/routing"
+
+# The base class for all application mailboxes. Not intended to be inherited from directly. Inherit from
+# `ApplicationMailbox` instead, as that's where the app-specific routing is configured. This routing
+# is specified in the following ways:
+#
+#   class ApplicationMailbox < ActionMailbox::Base
+#     # Any of the recipients of the mail (whether to, cc, bcc) are matched against the regexp.
+#     routing /^replies@/i => :replies
+#
+#     # Any of the recipients of the mail (whether to, cc, bcc) needs to be an exact match for the string.
+#     routing "help@example.com" => :help
+#
+#     # Any callable (proc, lambda, etc) object is passed the inbound_email record and is a match if true.
+#     routing ->(inbound_email) { inbound_email.mail.to.size > 2 } => :multiple_recipients
+#
+#     # Any object responding to #match? is called with the inbound_email record as an argument. Match if true.
+#     routing CustomAddress.new => :custom
+#
+#     # Any inbound_email that has not been already matched will be sent to the BackstopMailbox.
+#     routing :all => :backstop
+#   end
+#
+# Application mailboxes need to overwrite the `#process` method, which is invoked by the framework after
+# callbacks have been run. The callbacks available are: `before_processing`, `after_processing`, and
+# `around_processing`. The primary use case is ensure certain preconditions to processing are fulfilled
+# using `before_processing` callbacks.
+#
+# If a precondition fails to be met, you can halt the processing using the `#bounced!` method,
+# which will silently prevent any further processing, but not actually send out any bounce notice. You
+# can also pair this behavior with the invocation of an Action Mailer class responsible for sending out
+# an actual bounce email. This is done using the `#bounce_with` method, which takes the mail object returned
+# by an Action Mailer method, like so:
+#
+#   class ForwardsMailbox < ApplicationMailbox
+#     before_processing :ensure_sender_is_a_user
+#
+#     private
+#       def ensure_sender_is_a_user
+#         unless User.exist?(email_address: mail.from)
+#           bounce_with UserRequiredMailer.missing(inbound_email)
+#         end
+#       end
+#   end
+#
+# During the processing of the inbound email, the status will be tracked. Before processing begins,
+# the email will normally have the `pending` status. Once processing begins, just before callbacks
+# and the `#process` method is called, the status is changed to `processing`. If processing is allowed to
+# complete, the status is changed to `delivered`. If a bounce is triggered, then `bounced`. If an unhandled
+# exception is bubbled up, then `failed`.
+#
+# Exceptions can be handled at the class level using the familiar `Rescuable` approach:
+#
+#   class ForwardsMailbox < ApplicationMailbox
+#     rescue_from(ApplicationSpecificVerificationError) { bounced! }
+#   end
+class ActionMailbox::Base
+  include ActiveSupport::Rescuable
+  include ActionMailbox::Callbacks, ActionMailbox::Routing
+
+  attr_reader :inbound_email
+  delegate :mail, :delivered!, :bounced!, to: :inbound_email
+
+  delegate :logger, to: ActionMailbox
+
+  def self.receive(inbound_email)
+    new(inbound_email).perform_processing
+  end
+
+  def initialize(inbound_email)
+    @inbound_email = inbound_email
+  end
+
+  def perform_processing
+    track_status_of_inbound_email do
+      run_callbacks :process do
+        process
+      end
+    end
+  rescue => exception
+    # TODO: Include a reference to the inbound_email in the exception raised so error handling becomes easier
+    rescue_with_handler(exception) || raise
+  end
+
+  def process
+    # Overwrite in subclasses
+  end
+
+  def finished_processing?
+    inbound_email.delivered? || inbound_email.bounced?
+  end
+
+
+  def bounce_with(message)
+    inbound_email.bounced!
+    message.deliver_later
+  end
+
+  private
+    def track_status_of_inbound_email
+      inbound_email.processing!
+      yield
+      inbound_email.delivered! unless inbound_email.bounced?
+    rescue
+      inbound_email.failed!
+      raise
+    end
+end