If you are using MSGTAG on an email to the Ministry of Defence I would be very surprised indeed if you get a response. I would think it almost certain that the MOD servers are heavily protected against any programme that attempts to transmit itself without the users knowledge. I know I've got the MSGTAG IP blocked and no doubt the MOD has as well. In fact they've probably got it blocked before the email is delivered. Try again but this time without MSGTAG.