Land #6854, smtp header fix

Fixes an issue with duplicate headers when sending emails.

Fixes MS-1476

lib/msf/core/exploit/smtp_deliver.rb

@@ -163,8 +163,8 @@ module Exploit::Remote::SMTPDeliver
       print_error("Server refused our mail")
     else
       full_msg = ''
-      full_msg << date
-      full_msg << subject unless subject.nil?
+      full_msg << date unless data =~ /date: /i
+      full_msg << subject unless subject.nil? || data =~ /subject: /i
       full_msg << data
       send_status = raw_send_recv("#{full_msg}\r\n.\r\n", nsock)
     end

modules/auxiliary/client/smtp/emailer.rb

@@ -119,7 +119,6 @@ class MetasploitModule < Msf::Auxiliary
     datastore['MAILFROM'] = from
 
     msg       = load_file(msg_file)
-    email_sig = load_file(sig_file)
 
     if (type !~ /text/i and type !~ /text\/html/i)
       print_error("YAML config: #{type}")