I have a reason to do that.
I have recorded a voice message, attached with email, and sent it to several companies. One company, takes that voice message/email, and send it to millions of people.
I want to stop resend of my email/voice recording.
I am C# develop, one of my client asked me this question. I asked him to introduce verification codes, so that nobody will be able to listen the voice but still emails would be sent to millions of poeple.
Any workaround for this problem?