There should at least be a toggle where you can enable the ability to bypass the mail system when winning an auction via the "buy now" price, and have whatever you bought go directly into your inventory.
After all, it's not REALLY like you won an auction...getting something at its "buy now" price is much more akin to buying it from a vendor.
I just feel it's pointless to get "auction won" notifications in your mailbox when it's something you purchased 'straight up'.
Especially when buying 20 of some mat. It's about as frustrating as the email notification for being outbid on an item.