[root@mail ~]# telnet localhost 110
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
+OK <17451.1290275451@mail.viet-cntt.com>
user <a href="mailto:user1@viet-cntt.com">user1@viet-cntt.com</a>
+OK
pass 121212
-ERR unable to write pipe
Connection closed by foreign host.

[root@mail ~]# tail /var/log/qmail/qmail-pop3d/current
@400000004ce803c001eb4b7c tcpserver: status: 1/100
@400000004ce803c001eba554 tcpserver: pid 17333 from 127.0.0.1
@400000004ce803c11f43d284 tcpserver: ok 17333 :127.0.0.1:110 :127.0.0.1::60222
@400000004ce803d511d3d1e4 tcpserver: end 17333 status 256
@400000004ce803d511d56c0c tcpserver: status: 0/100
@400000004ce80a8320ab3e3c tcpserver: status: 1/100
@400000004ce80a8320b5870c tcpserver: pid 17451 from 127.0.0.1
@400000004ce80a851deaa354 tcpserver: ok 17451 :127.0.0.1:110 :127.0.0.1::54813
@400000004ce80a950e05c66c tcpserver: end 17451 status 256
@400000004ce80a950e05ce3c tcpserver: status: 0/100