use 'reply_by_email_address' setting for handling bounce emails using VERP

config/locales/server.en.yml

@@ -819,7 +819,6 @@ en:
     title: "The name of this site, as used in the title tag."
     site_description: "Describe this site in one sentence, as used in the meta description tag."
     contact_email: "Email address of key contact responsible for this site. Used for critical notifications such as unhandled flags, as well as on the /about contact form for urgent matters."
-    bounce_email: "Variable Email Return Path used for emails, example: bounce@example.com will cause us to generate bounce+GUID@example.com as the Return Path for emails we send. This feature allows us to automatically disable bouncing emails. Requires additional configurations, leave blank if unsure."
     contact_url: "Contact URL for this site. Used on the /about contact form for urgent matters."
     queue_jobs: "DEVELOPER ONLY! WARNING! By default, queue jobs in sidekiq. If disabled, your site will be broken."
     crawl_images: "Retrieve images from remote URLs to insert the correct width and height dimensions."

config/site_settings.yml

@@ -26,10 +26,6 @@ required:
     client: true
     default: ''
     type: email
-  bounce_email:
-    default: ''
-    type: email
-    shadowed_by_global: true
   contact_url:
     client: true
     default: ''

lib/email/sender.rb

@@ -116,16 +116,13 @@ module Email
         @message.header['List-Post'] = "<mailto:#{email}>"
       end
 
-      unless SiteSetting.bounce_email.blank?
+      if SiteSetting.reply_by_email_address.present? && SiteSetting.reply_by_email_address["+"]
         email_log.bounce_key = SecureRandom.hex
-        address,domain = SiteSetting.bounce_email.split('@')
-        address << (address =~ /[+]/ ? "-" : '+')
-        address << email_log.bounce_key
 
         # WARNING: RFC claims you can not set the Return Path header, this is 100% correct
         # however Rails has special handling for this header and ends up using this value
         # as the Envelope From address so stuff works as expected
-        @message.header[:return_path] = "#{address}@#{domain}"
+        @message.header[:return_path] = SiteSetting.reply_by_email_address.sub("%{reply_key}", "verp-#{email_log.bounce_key}")
       end
 
       email_log.post_id = post_id if post_id.present?

spec/components/email/sender_spec.rb

@@ -77,25 +77,21 @@ describe Email::Sender do
       email_sender.send
     end
 
-    context "adds return_path correctly when no plus addressing" do
-      before do
-        SiteSetting.bounce_email = 'bounce@test.com'
-      end
+    context "doesn't add return_path when no plus addressing" do
+      before { SiteSetting.reply_by_email_address = '%{reply_key}@test.com' }
 
       When { email_sender.send }
       Then {
-        expect(message.header[:return_path].to_s).to eq("bounce+#{EmailLog.last.bounce_key}@test.com")
+        expect(message.header[:return_path].to_s).to eq("")
       }
     end
 
-    context "adds return_path correctly with plus addressing" do
-      before do
-        SiteSetting.bounce_email = 'bounce+meta@test.com'
-      end
+    context "adds return_path with plus addressing" do
+      before { SiteSetting.reply_by_email_address = 'replies+%{reply_key}@test.com' }
 
       When { email_sender.send }
       Then {
-        expect(message.header[:return_path].to_s).to eq("bounce+meta-#{EmailLog.last.bounce_key}@test.com")
+        expect(message.header[:return_path].to_s).to eq("replies+verp-#{EmailLog.last.bounce_key}@test.com")
       }
     end