What is Best Offer feature
It would let auctioneer receive offers for its auction. So, users can place bids but if someone wants to offer a price that user can send that price offer to auctioneer. Once he sends it, auctioneer can accept or reject it.
When he accepts, auction expires and user receives a payment link to pay for the auction
When he rejects it, user receives rejection email and he can again send offer.
How does it work.
Admin and sellers can activate BEST OFFER feature while adding their specific auction.
Admin can configure to send email alerts to users upon acceptance and rejection. He can do it by going to WP admin panel -> Ultimate Auction Pro -> Emails -> Best Offer Accept OR Best Offer Reject