Windows 2000 and Microsoft Post Office

In both Windows 95 and 98, there was a program which enabled interoffice mail called Microsoft Post Office. It is a water-down version of MS Exchange.
Can Windows 2000 run the same program or does it have
an equivalent? All the the computers withW95 and W98 are able to use this inner office postoffice.
It uses Outlook. The computers with Windows 2000 can not access this presently without adding some equivalent program.