Win-based network (LAN manager) uses netbios protocol to resolve names. It works via broadcast on local segment of LAN. Bridges and such stuff are transparent for broadcast, but throu gh internet, you never pass such Ethernet related packet. For this, there is a service named WINS (Windows Internet Name Serving), which stores pairs netbios-name/ip address . Configure your Samba server and your client to use this service. Samba can use it's own WINS server, or can be a client. It can also use DNS for resolving netbios names. Keywords: wins support, wins server, dns proxy in your smb.conf file
Well and make sure your IP provider is not filtering netbios services.