Store overriden to, cc, bcc values in X- headers

lib/mail/network/delivery_methods/override_recipient_smtp.rb

@@ -21,6 +21,16 @@ module Mail
   #     delivery_method :override_recipient_smtp,
   #       :to => ['[email protected]', '[email protected]']
   #   end
+  #
+  # === Debug
+  #
+  # The original to, cc, and bcc fields are stored in these custom email headers
+  # for debugging:
+  #
+  #   X-Override-To
+  #   X-Override-Cc
+  #   X-Override-Bcc
+  #
   class OverrideRecipientSMTP < Mail::SMTP
     def initialize(values)
       unless values[:to]
@@ -31,11 +41,29 @@ def initialize(values)
     end
 
     def deliver!(mail)
+      store_in_custom_headers(mail)
+
       mail.to = settings[:to]
       mail.cc = nil
       mail.bcc = nil
 
       super(mail)
     end
+
+    private
+
+    def store_in_custom_headers(mail)
+      {
+        'X-Override-To' => mail.to,
+        'X-Override-Cc' => mail.cc,
+        'X-Override-Bcc' => mail.bcc
+      }.each do |header, addresses|
+        if addresses
+          addresses.each do |address|
+            mail.header = "#{mail.header}\n#{header}: #{address}"
+          end
+        end
+      end
+    end
   end
 end

spec/mail/network/delivery_methods/override_recipient_smtp_spec.rb

@@ -23,9 +23,13 @@
     end
 
     response = mail.deliver!
+
     response.to.should eq ['[email protected]']
     response.cc.should eq []
     response.bcc.should eq []
+    response.header['X-Override-To'].to_s.should eq '[[email protected], [email protected]]'
+    response.header['X-Override-Cc'].to_s.should eq '[email protected]'
+    response.header['X-Override-Bcc'].to_s.should eq '[email protected]'
   end
 
   it 'can accept an array as configuration' do
@@ -39,6 +43,7 @@
     end
 
     response = mail.deliver!
+
     response.to.should eq ['[email protected]', '[email protected]']
   end
 end