To work around this, you can disable the Allow client-to-client file transfer in the Policy administration page. This will mean all file transfers go via the Sametime server and won't be p2p. You will need to restart your Sametime server for the change to take effect.
For further details, search the Lotus support site. www.lotus.com/support


. . RE: Sametime file transfer with NAT... (Carl Tyler 10.Dec.10) 