I have setup POP3 on a Groupwise 6.5 server. I have no problems sending or receiving email inside the network using Outlook or Outlook Express. If I go outside the network and use Outlook or Outlook Express, I can send mail to anyone on the outside, I can receive mail from people on the inside of the network or outside the network, but I cannot send to anyone on the inside or reply to a message that they have sent me.
I tried adding an exception to the SMTP Relay settings to include the domain POP3 is setup on. I added an MX record to the Internal DNS server. Very weird and not sure why I can't send to anyone that is on the same domain as the POP3/Groupwise server.