DynaDot and GoDaddy have recently tried to implement changes to make more expired domain auctions complete, and not have owners intentionally let domains expire just to renew them at the last moment.
At name.com, we receive expired domain purchases instantly upon purchase (they deliver 100% of won expired auctions).
Have you considered changing your expired domain auctions system? For example, instead of running a 25 day auction, how about doing 5 day or 10 day auctions starting on day 26, where the domain will always be delivered to buyer? Or extending the auction time to 30 days, where former owners can only renew the domain on the first 25 days? Right now the system is set up in a way so that more domains that get bids get renewed than what I have seen on any other platform.
Sending notification emails to former owners telling them that their domain is getting bid on also seems to invite domainers to let their names expire to let the market determine whether any of them have value, and then renew all of those that get bids. Many users are clearly abusing the system to let the "crowd" determine which of their domains are perceived to have value, and then proceed to renew all of those. I saw one guy let something like 30 domains based around a new tech expire. I bid on two of them. He renewed those two and let the other 28 that didn't get bids expire. There is a lot of activity like this. Also, domainers let valuable domains expire, they get bid on ($X,XXX), and then renewed at the last moment. This is just a way of drawing attention to their domains, in the hopes that the same people bidding will come to them after they have renewed the domain and attempt to acquire it from them privately. All these games played by people who let their domain expire with the intention of renewing them wastes a lot of time for legit bidders who spend time researching and bidding on these expired domains.
