diff --git a/lib/email/sender.rb b/lib/email/sender.rb
index 14f249f3362..d1720aedd98 100644
--- a/lib/email/sender.rb
+++ b/lib/email/sender.rb
@@ -117,9 +117,9 @@ module Email
       email_log.reply_key = reply_key if reply_key.present?
 
       # Remove headers we don't need anymore
-      @message.header['X-Discourse-Topic-Id'] = nil
-      @message.header['X-Discourse-Post-Id'] = nil
-      @message.header['X-Discourse-Reply-Key'] = nil
+      @message.header['X-Discourse-Topic-Id'] = nil if topic_id.present?
+      @message.header['X-Discourse-Post-Id'] = nil if post_id.present?
+      @message.header['X-Discourse-Reply-Key'] = nil if reply_key.present?
 
       # Suppress images from short emails
       if SiteSetting.strip_images_from_short_emails && @message.html_part.body.to_s.bytesize <= SiteSetting.short_email_length && @message.html_part.body =~ /<img[^>]+>/
diff --git a/spec/components/email/sender_spec.rb b/spec/components/email/sender_spec.rb
index e8d34b38f65..55f56e4c351 100644
--- a/spec/components/email/sender_spec.rb
+++ b/spec/components/email/sender_spec.rb
@@ -87,6 +87,24 @@ describe Email::Sender do
       Then { expect(message.header['Precedence']).to be_present }
     end
 
+    context "removes custom Discourse headers from topic notification mails" do
+      before do
+        message.header['X-Discourse-Topic-Id'] = 5577
+      end
+
+      When { email_sender.send }
+      Then { expect(message.header['X-Discourse-Topic-Id']).not_to be_present }
+      Then { expect(message.header['X-Discourse-Post-Id']).not_to be_present }
+      Then { expect(message.header['X-Discourse-Reply-Key']).not_to be_present }
+    end
+
+    context "removes custom Discourse headers from digest/registration/other mails" do
+      When { email_sender.send }
+      Then { expect(message.header['X-Discourse-Topic-Id']).not_to be_present }
+      Then { expect(message.header['X-Discourse-Post-Id']).not_to be_present }
+      Then { expect(message.header['X-Discourse-Reply-Key']).not_to be_present }
+    end
+
     context 'email logs' do
       let(:email_log) { EmailLog.last }