I get a whole bunch of Nigerian email scam emails a day, and they all have something in common, among other things: They all ask you to respond to a different email address than the one they originally emailed you from. Any reason why they do this? Tracking purposes?
Simple. They never sent it from the email address that appears in the ‘from’ field. There’s no verification whatsoever that what somebody claims to be their originating address is real. This dates from the time when the only people sending emails were a few computer geeks, and the idea of transnational identity fraud via email would have seemed (perhaps) laughable.
More than once, when the address they’ve requested the reply to has been an easily-identifiable one, I’ve forwarded it to abuse@xyz.com, and once I received a reply from them, thanking me for the help.
I think you will find that one of the primary reasons is that the email addy from which these emails are sent is shut down by Hotmail (or whoever) very rapidly, so the scammers need another (working) email address to receive replies.