Bounces being forwarded to wrong folder

We use LSMTP to send our newsletters and process bounces. We have it set
up to forward bounces coming back from newsletter(_at_)lifescript(_dot_)com to
bounces(_at_)lifescript(_dot_)com(_dot_)
We have our return-path as bounces(_at_)lifescript(_dot_)com but for some 
reason,
the newsletters sent to hotmail are being bounced back to
service(_at_)lifescript(_dot_)com after we setup an SPF record.
Any idea why?