diff --git a/app/mailers/user_notifications.rb b/app/mailers/user_notifications.rb
index 85ef806c9d9..481f87704d4 100644
--- a/app/mailers/user_notifications.rb
+++ b/app/mailers/user_notifications.rb
@@ -107,13 +107,10 @@ class UserNotifications < ActionMailer::Base
       url: @post.url,
       username: username,
       add_unsubscribe_link: true,
+      allow_reply_by_email: opts[:allow_reply_by_email],
       template: "user_notifications.user_#{notification_type}"
     }
 
-    if opts[:allow_reply_by_email] && SiteSetting.reply_by_email_enabled?
-      email_opts[:allow_reply_by_email] = true
-    end
-
     # If we have a display name, change the from address
     if username.present?
       email_opts[:from_alias] = I18n.t(:via, username: username, site_name: SiteSetting.title)
diff --git a/app/models/email_log.rb b/app/models/email_log.rb
index 9e6e05613c6..4c3b9de8201 100644
--- a/app/models/email_log.rb
+++ b/app/models/email_log.rb
@@ -3,13 +3,6 @@ class EmailLog < ActiveRecord::Base
   validates_presence_of :email_type
   validates_presence_of :to_address
 
-  before_create do
-    # We only generate a reply
-    if SiteSetting.reply_by_email_enabled?
-      self.reply_key = SecureRandom.hex(16)
-    end
-  end
-
   after_create do
     # Update last_emailed_at if the user_id is present
     User.update_all("last_emailed_at = CURRENT_TIMESTAMP", id: user_id) if user_id.present?
diff --git a/lib/email/message_builder.rb b/lib/email/message_builder.rb
index b74499d29c4..7aed31e817e 100644
--- a/lib/email/message_builder.rb
+++ b/lib/email/message_builder.rb
@@ -35,6 +35,10 @@ module Email
       body
     end
 
+    def allow_reply_by_email?
+      SiteSetting.reply_by_email_enabled? && @opts[:allow_reply_by_email]
+    end
+
     def template_args
       @template_args ||= { site_name: SiteSetting.title,
                            base_url: Discourse.base_url,
@@ -60,6 +64,9 @@ module Email
       if @opts[:add_unsubscribe_link]
         result['List-Unsubscribe'] = "<#{template_args[:user_preferences_url]}>" if @opts[:add_unsubscribe_link]
       end
+
+      result['Discourse-Reply-Key'] = SecureRandom.hex(16) if allow_reply_by_email?
+
       result
     end
 
diff --git a/lib/email/sender.rb b/lib/email/sender.rb
index d0ffc31a9aa..5f23dba9ce3 100644
--- a/lib/email/sender.rb
+++ b/lib/email/sender.rb
@@ -42,7 +42,13 @@ module Email
       to_address = @message.to
       to_address = to_address.first if to_address.is_a?(Array)
 
-      EmailLog.create!(email_type: @email_type, to_address: to_address, user_id: @user.try(:id))
+      email_log = EmailLog.new(email_type: @email_type, to_address: to_address, user_id: @user.try(:id))
+
+      reply_key = @message.header['Discourse-Reply-Key'].to_s
+      email_log.reply_key = reply_key if reply_key.present?
+      email_log.save!
+      email_log
+
     end
 
   end
diff --git a/spec/components/email/message_builder_spec.rb b/spec/components/email/message_builder_spec.rb
index 973cca81e87..a392fcb7afe 100644
--- a/spec/components/email/message_builder_spec.rb
+++ b/spec/components/email/message_builder_spec.rb
@@ -25,6 +25,42 @@ describe Email::MessageBuilder do
     expect(builder.build_args[:charset]).to eq("UTF-8")
   end
 
+  context "reply by email" do
+
+    context "without allow_reply_by_email" do
+      it "does not have a Discourse-Reply-Key" do
+        expect(builder.header_args['Discourse-Reply-Key']).to be_blank
+      end
+    end
+
+    context "with allow_reply_by_email" do
+      let(:reply_by_email_builder) { Email::MessageBuilder.new(to_address, allow_reply_by_email: true) }
+      let(:reply_key) { reply_by_email_builder.header_args['Discourse-Reply-Key'] }
+
+      context "With the SiteSetting enabled" do
+        before do
+          SiteSetting.expects(:reply_by_email_enabled?).returns(true)
+        end
+
+        it "has a Discourse-Reply-Key" do
+          expect(reply_key).to be_present
+          expect(reply_key.size).to eq(32)
+        end
+      end
+
+      context "With the SiteSetting disabled" do
+        before do
+          SiteSetting.expects(:reply_by_email_enabled?).returns(false)
+        end
+
+        it "has no Discourse-Reply-Key" do
+          expect(reply_key).to be_blank
+        end
+      end
+    end
+
+  end
+
   context "unsubscribe link" do
 
     context "with add_unsubscribe_link false" do
diff --git a/spec/components/email/sender_spec.rb b/spec/components/email/sender_spec.rb
index c2a693c26ed..f557a584428 100644
--- a/spec/components/email/sender_spec.rb
+++ b/spec/components/email/sender_spec.rb
@@ -22,6 +22,8 @@ describe Email::Sender do
 
   context 'with a valid message' do
 
+    let(:reply_key) { "abcd" * 8 }
+
     let(:message) do
       message = Mail::Message.new to: 'eviltrout@test.domain',
                                   body: '**hello**'
@@ -37,49 +39,33 @@ describe Email::Sender do
     end
 
     context 'email logs' do
+      let(:email_log) { EmailLog.last }
 
-      before do
-        email_sender.send
-        @email_log = EmailLog.last
-      end
-
-      it 'creates an email log' do
-        @email_log.should be_present
-      end
-
-      it 'has the correct type' do
-        @email_log.email_type.should == 'valid_type'
-      end
-
-      it 'has the correct to_address' do
-        @email_log.to_address.should == 'eviltrout@test.domain'
-      end
-
-      it 'has no user_id' do
-        @email_log.user_id.should be_blank
-      end
-
-
+      When { email_sender.send }
+      Then { expect(email_log).to be_present }
+      Then { expect(email_log.email_type).to eq('valid_type') }
+      Then { expect(email_log.to_address).to eq('eviltrout@test.domain') }
+      Then { expect(email_log.reply_key).to be_blank }
+      Then { expect(email_log.user_id).to be_blank }
     end
 
+    context "email log with a reply key" do
+      before do
+        message.header['Discourse-Reply-Key'] = reply_key
+      end
+
+      let(:email_log) { EmailLog.last }
+      When { email_sender.send }
+      Then { expect(email_log.reply_key).to eq(reply_key) }
+    end
+
+
     context 'email parts' do
-      before { email_sender.send }
-
-      it 'makes the message multipart' do
-        message.should be_multipart
-      end
-
-      it 'sets the correct content type for the plain text part' do
-        expect(message.text_part.content_type).to eq 'text/plain; charset=UTF-8'
-      end
-
-      it 'sets the correct content type for the html part' do
-        expect(message.html_part.content_type).to eq 'text/html; charset=UTF-8'
-      end
-
-      it 'converts the html part to html' do
-        expect(message.html_part.body.to_s).to match("<p><strong>hello</strong></p>")
-      end
+      When { email_sender.send }
+      Then { expect(message).to be_multipart }
+      Then { expect(message.text_part.content_type).to eq('text/plain; charset=UTF-8') }
+      Then { expect(message.html_part.content_type).to eq('text/html; charset=UTF-8') }
+      Then { expect(message.html_part.body.to_s).to match("<p><strong>hello</strong></p>") }
     end
   end
 
diff --git a/spec/mailers/user_notifications_spec.rb b/spec/mailers/user_notifications_spec.rb
index 31afe29879c..ea1a25943bb 100644
--- a/spec/mailers/user_notifications_spec.rb
+++ b/spec/mailers/user_notifications_spec.rb
@@ -50,27 +50,14 @@ describe UserNotifications do
   shared_examples "supports reply by email" do
     context "reply_by_email" do
       it "should have allow_reply_by_email set when that feature is enabled" do
-        SiteSetting.stubs(:reply_by_email_enabled?).returns(true)
         expects_build_with(has_entry(:allow_reply_by_email, true))
       end
-
-      it "should have not allow_reply_by_email set when that feature is disabled" do
-        SiteSetting.stubs(:reply_by_email_enabled?).returns(false)
-        expects_build_with(Not(has_entry(:allow_reply_by_email, true)))
-      end
     end
   end
 
   shared_examples "no reply by email" do
     context "reply_by_email" do
-
-      it "doesn't support reply by email, even when that option is enabled" do
-        SiteSetting.stubs(:reply_by_email_enabled?).returns(true)
-        expects_build_with(Not(has_entry(:allow_reply_by_email, true)))
-      end
-
-      it "should have not allow_reply_by_email set when that feature is disabled" do
-        SiteSetting.stubs(:reply_by_email_enabled?).returns(false)
+      it "doesn't support reply by email" do
         expects_build_with(Not(has_entry(:allow_reply_by_email, true)))
       end
     end
@@ -131,7 +118,6 @@ describe UserNotifications do
     end
   end
 
-
   describe "user quoted" do
     include_examples "notification email building" do
       let(:notification_type) { :quoted }
diff --git a/spec/models/email_log_spec.rb b/spec/models/email_log_spec.rb
index 7267f8eca01..51cf7d4077b 100644
--- a/spec/models/email_log_spec.rb
+++ b/spec/models/email_log_spec.rb
@@ -10,40 +10,6 @@ describe EmailLog do
 
   context 'after_create' do
 
-    context "reply_key" do
-
-      context "with reply by email enabled" do
-        before do
-          SiteSetting.expects(:reply_by_email_enabled).returns(true)
-        end
-
-        context 'generates a reply key' do
-          let(:reply_key) { Fabricate(:email_log).reply_key }
-
-          it "has a reply key" do
-            expect(reply_key).to be_present
-            expect(reply_key.size).to eq(32)
-          end
-        end
-      end
-
-      context "with reply by email disabled" do
-        before do
-          SiteSetting.expects(:reply_by_email_enabled).returns(false)
-        end
-
-        context 'generates a reply key' do
-          let(:reply_key) { Fabricate(:email_log).reply_key }
-
-          it "has no reply key" do
-            expect(reply_key).to be_blank
-          end
-        end
-      end
-
-    end
-
-
     context 'with user' do
       let(:user) { Fabricate(:user) }