If suppose I send a message from my organisation to say 10 users with different email ids saying that "There is a contest which will give you 500$ if u forward this email to 10 people at least whose ids dont exist in the database" then how am i supposed to keep a track of all the email ids after the 10 ids that i forwarded and how am I supposed to trap the 500th person or the last person or any forwaded ids for that matter.