remote login to linux host?

[Jan van Veldhuizen]

I have cygwin installed on my XP, and I can succesfully login to my host if
I am home.
I use 'xwin -query <host>'.
If I am outside the network and try it over the internet I get only the grey
Xwin screen.
First I thought my NAT and firewall was blocking, but that is not true. I
defined my linux host as defserver in my NAT, so everything is routed to the
host. Telnetting is okay, I can use SWAT to remotely manage samba, VNC
works, only cygwin refuses to show my login screen...

What could be wrong?