Outlook 2000 Shared Calendar

I have several users on a small W2K Domain. They all use Outlook 2000 for POP3 email. They don't have any enterprise email. Everything comes from their outside email server. On one workstation I setup outlook to share the calendar. It sent out the notifications, everybody replied with 'Accept' but nobody's changes to the calendar seem to get added. I have it set to send changes every 5 minutes. Will calendar sharing work over POP3? What am I missing? Even items added to the calendar bythe owner, at his own workstation don't show up on other users copy of that calendar. Any help is appreciated.

Brian