Browsing has its limitations and the PC maintains only one list to the workgroup/domain, where it belongs to. This doesn't change with Dial-Up Networking. If you logon to a NT domain named DOMAIN with a client which belongs to a workgroup named WORKGROUP, then the client will maintain the browser list for the WORKGROUP only. That might be one of the reasons why you don't see any computers on the network. I don't know much about Lotus Notes Clients, but I'm guessing that the client has the server name or IP address somewhere in its configuration and that is why it is able to find the server.
There are couple of things you can do to browse the remote network. On the client side ensure that the PC belongs to a workgroup named as the name of the remote domain. For example if the remote domain name is DOMAIN, then the client should belong to a workgroup named DOMAIN. As the previous poster mentioned, you could also add the WINS address, if you have any, to the LMHOST file.
On the server side, I like to insta