After having problems with unresponsiveness with qpop3.1, I upgraded to 4.0 Now I am still getting unexpected connection terminations. I see a lot of " I/O error flushing output to client" and "-ERR POP EOF or I/O Error".
I don't know where to go with this, but a lot of people are complaining.
In my experience, this is not a Qpopper problem at all - all it is, is Qpopper reported that the TCP connection has been closed unexpectedly. So it is just Qpopper reporting a problem that lies elsewhere.
There are many possible reasons for this, but by far the most common is simply users with phoneline/modem problems, you'll typically see this message if their modem disconnects while they're downloading, and then the TCP session times out and then closes.
Try correlating these errors with your dialup logs to see if the user in question had their modem hang up at the time.
Really noisy phone lines that cause their modem to keep retraining can also cause this timeout.
One further problem I've noted that can cause it, is certain kinds of corrupted messages trigger a bug in some versions of Outlook Express that basically make it stop and wait in the middle of downloading, and then time out. In this case it will always happen at the same point. The only solution (apart from them changing to a real email program :) is to delete the offending message for them, or get them to delete it through a webmail interface.
Regards, Simon
