> Hi, This has happened again!
> This time, server restarted due to network issues and VPOP wouldn't start with same issue.
> I tried just removing VPOP3.pid and started.dat then reboot but it still failed to start so I deleted dbcheck.txt and _database/bayes.ldb folder and
> Working again!
If the bayes.ldb database is corrupted, that will cause VPOP3 to crash. Current versions should automatically recover from that (by automatically deleting the folder and then recreating it). It's Google's LevelDB database which is very fast, but, unfortunately renowned for getting corrupted if the PC is powered off/restarted without being shutdown (https://en.wikipedia.org/wiki/LevelDB#Bugs_and_reliability). Recent versions should recover from that automatically. Older versions couldn't recover automatically (we'd naively assumed that since it was written by Google, and is used in the Chrome browser, it'd be reliable).
> The client is not impressed, is there any guarantee that if we pay for the upgrade it will fix it? They are on V6.16
We can't guarantee they won't have problems. v6.16 is about 3 years old now and we haven't had any of this type of problem reported with more recent versions. We run many instances of VPOP3 for our Hosted Service and have never had this problem ourselves. But that doesn't mean that it's impossible for a new way to cause VPOP3 a problem to appear.
The upgrade cost is not expensive. If they want, we can cancel & refund the upgrade if the same problem occurs, but they'll have to restore from backup if they want to go back to the older version because downgrading to older versions is not a supported scenario.