I'm not familiar with DPop, but try doing this (i'm assuming you're using sockets to do this)
get a packet sniffer. If you are using a program to connect to this server usually (in the case of getting pop email, i will use a mail client.. duh) fire that up as well.
start logging packets and then check your email. once the operation is completed, stop logging packets and analyze the traffic. you can see what packets are sent and received and in what order. You should then connect to the Dpop server using telnet and experiment with commands and get that correct. Now you can translate that to PHP code..
p.
