At one point last year the DSBL blacklist, quite popular in it’s hayday, lost it’s entire database in a RAID system crash. The name servers kept on answering requests in the meantime. Yesterday, this activity stopped.
This means that if you still use the DSBL, you might be delaying or bouncing your inbound mail. Check your servers and make sure the DSBL is not listed. In short, everything with *.dsbl.org must go.
Note: We have not / do not use DSBL in ExchangeDefender so if you are with us, you were not affected.