If Paypal decides that the FROM will permanently be firstname.lastname@example.org, then they could add an additional mail header called Reply-To: and put the buyer’s email in there. While whether a Reply-To is recognized depends on the web mail client, desktop e-mail client, or smartphone e-mail client used… most modern e-mail clients will know how to handle this.
PayPal made what at first glance appears to be a minor change in the way it sends payment notice emails to sellers, but it’s having a huge impact on some sellers’ operations, and merchants discussed the issue on various online discussion boards throughout the day on Wednesday.
Normally when PayPal sends merchants a “Notification of payment received” email, the “From” field is populated by the buyer’s email address. As of late Tuesday evening, PayPal switched the protocol to enter the static email address “email@example.com” in the “From” field rather than the buyer’s email address. – http://www.auctionbytes.com/cab/cab/abn/y12/m01/i26/s02