When you attempt to transfer a file to another Windows Messenger client, you receive:
We could not send this file because the connection is blocked. Please contact your network administrator or Internet service provider; they may be able to enable file transfers.
The other client may receive:
You have failed to receive the file <file_name> from <sending_user>.
This problem occurs with any of the following providers:
The Microsoft Network (MSN) provider
The Exchange provider
The Session Initiation Protocol provider
When you are using a VPN connection, the Windows Messenger client may send the IP address of your LAN connection. If the other client cannot access this LAN connection, the error occurs.
To make Windows Messenger return the IP address of the VPN connection, move the VPN connection above the LAN connection in the binding order. See tip 2743 » How do I change the Binding Order in Windows 2000?