MS Exchange 5.5 server -mail transfer

The MS exhange server is running on windows NT4.0. The modem(33Kbps d-link) is configured to dial a remote exchange server with similar configuration.The remote location gets dialed (modem is initiated). The mail gets into the sender’s que, but is not deliverd to the remote server.Thus no mail is transferred.
However on a lan connection (No modem for remote) the same setup works for mail transfer