Land rapid7#4758, SMTPDeliver DATA header fix

Author: wvu

lib/msf/core/exploit/smtp_deliver.rb

@@ -141,6 +141,8 @@ def send_message(data)
     raw_send_recv("MAIL FROM: <#{datastore['MAILFROM']}>\r\n", nsock)
     raw_send_recv("RCPT TO: <#{datastore['MAILTO']}>\r\n", nsock)
 
+    resp = raw_send_recv("DATA\r\n", nsock)
+
     # If the user supplied a Date field, use that, else use the current
     # DateTime in the proper RFC2822 format.
     if datastore['DATE'].present?
@@ -154,8 +156,6 @@ def send_message(data)
       raw_send_recv("Subject: #{datastore['SUBJECT']}\r\n", nsock)
     end
 
-    resp = raw_send_recv("DATA\r\n", nsock)
-
     # Avoid sending tons of data and killing the connection if the server
     # didn't like us.
     if not resp or not resp[0,3] == '354'