If you haven't already, try enabling debug logging and see if says anything helpful.
To enable tracing in Qpopper: 1. Do a 'make clean' 2. Re-run ./configure, adding '--enable-debugging'. 3. Edit the inetd.conf line for Qpopper, adding '-d' or '-t <tracefile-path>'. 4. Send inetd (or xinetd) a HUP signal. (Steps 3 and 4 are only needed if you use inetd (or xinetd). In standalone mode, you can add '-d' or '-t <tracefile-path>' to the command line directly.) (In either standalone or inetd mode, if you use a configuration file you can add 'set debug' or 'set tracefile = <tracefile>' to either a global or user-specific configuration file instead of steps 3 and 4.) This causes detailed tracing to be written to the syslog or to the file specified as 'tracefile'. --
