nanoStream3 supports RTMPT, the tunneling protocol of RTMP,
including automatic Proxy detection.
The URL should then be similar to this:
rtmpt://server:port/live+streamID
The port should probably be 80, dependent on the corporate firewall and streaming server setup.
Please note that RTMPT Tunneling is a workaround
using the firewall-accepted HTTP protocol.
This requires a protocol overhead, so plain RTMP is preferred.
For using Firewalls, it might work to stream plain RTMP over port 80, like this:
rtmp://server:80/live+streamID
If this fails, use RTMPT.