Microsoft Mail Issue

[benci]

I hope I am not in the wrong forum with this thread. I have my Microsoft Mail residing in a WinNT 4 server. When I try to add a new user it gives me the error: "That action could not be completed. Check that your post office has sufficient disk space and your network connection is alive."
There is plenty of network space and the network connection is runnung.
Any ideas!?
Thank you