remove altering of custom headers

lib/postmark/message_extensions/mail.rb

@@ -143,10 +143,8 @@ def export_headers
       [].tap do |headers|
         self.header.fields.each do |field|
           key, value = field.name, field.value
-          next if bogus_headers.include? key.downcase
-          name = key.split(/-/).map { |i| i.capitalize }.join('-')
-
-          headers << { "Name" => name, "Value" => value }
+          next if reserved_headers.include? key.downcase
+          headers << { "Name" => key, "Value" => value }
         end
       end
     end
@@ -173,7 +171,7 @@ def export_native_attachments
       end
     end
 
-    def bogus_headers
+    def reserved_headers
       %q[
         return-path  x-pm-rcpt
         from         reply-to

spec/unit/postmark/message_extensions/mail_spec.rb

@@ -33,7 +33,7 @@
     end
   end
 
-  let(:mail_message_with_bogus_headers) do
+  let(:mail_message_with_reserved_headers) do
     mail_message.header['Return-Path'] = '[email protected]'
     mail_message.header['From'] = '[email protected]'
     mail_message.header['Sender'] = '[email protected]'
@@ -237,7 +237,7 @@
   end
 
   describe "#export_headers" do
-    let(:headers) { mail_message_with_bogus_headers.export_headers }
+    let(:headers) { mail_message_with_reserved_headers.export_headers }
     let(:header_names) { headers.map { |h| h['Name'] } }
 
     specify { expect(header_names).to include('Allowed-Header') }