I get many payment confirmation emails from paypal.  

In the actual header

From: So and So via Paypal

reply-to: *** Email address is removed for privacy ***

Outlook client correctly labels the first one as

From: So and So via Paypal

but the next half a dozen that came in about the same time are ALSO labelled identically as 

From: So and So via Paypal

when their email headers are in fact 

From: Somebody Else via Paypal

reply-to: *** Email address is removed for privacy ***

( etc, etc) 

?????!?!!???

Why is Outlook Mislabeling these in batches??

Paypal suggested that somehow these people are getting into my Address book mislabeled - but I cannot find any of them in my address book.

This only started a couple of weeks ago... and strangely the problem is identical on Mac and on Windows