This is from eBay:

Due to changes being made by email service providers to combat spam and spoof, eBay has changed the FROM address of member to member messages (Ask Seller A Question, Contact eBay Member, Reply to Question, etc.) to comply with emerging sender authentication standards and ensure delivery of these important messages into the inbox. To learn more about this change, please read this discussion thread on our Technical Issues board.

There's a large thread after this message. Click here to read it.

Many seller's feel that this is part of eBay's growing need to control communication between sellers and their buyers, which isn't in-line with their claim that eBay is "just a venue." This small announcement might have big impact for you, so take a look at the thread, and read the input there from other sellers.

http://forums.ebay.com/db2/thread.jspa?threadID=200086007&start=0&ssPageName=CMDV:AB