Path not found–Win95 and Win2000

I am having a problem with 4 machines(all DELL, 3 running 2000 and 1 with 98) not being able to access a MICROSOFT MAIL post office running on a win95 machine. 20 other machines on our network have no problem, but these four machines get the CAN NOTACCESS and PAth not found, even though I can see the machine on the network neighborhood and other machines on the network have no problems.. HELP!?