I am on .141/5.0 hybrid and don't have this problem, thank goodness. Feel sorry for those that do. Sometimes it's really annoying for clients who you know don't like too many e-mails.
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the phone doesn't "send" anything, the BIS servers create them based on settings between the BIS profile and the email acct.
to clarify "sending"
nothing goes from point A (your phone) to point B (another email acct)...they go from your phone (A) through the carrier's network (B) to BIS servers (C) to your email provider's servers (D), to the reciepien'ts email provider's servers (E) at minium. if there were notifications being created, they'd most likely come from C or D.
its possible that the incoming message is requesting the read recipt also, didn't think of that in my scenario before. but the settings in your BIS profile and email service provider's profile should override any request of a read/delievery notification.