What version of SNA server are you using?
SNA server version 3 and higher support tn3270/tn3270e (for mainframe connectivity) and tn5250 (for as/400 connectivity) clients. The ms windoes telnet client does not support those protocols so you need a 3270 and/or 5250 emulator from another vendor, such as NetManage or Hummingbird.
This assumes that you have a routed network between your workstation and the sna server.
If your network is bridged, then you need to use an emulator that works with the native sna protocol, as the sna server supports that as well. The NetManage and Hummingbird emulators will work in this case too.
Try to use the tn3270/tn5250 as the first choice as it does not require a bridged backbone. SNA is not a routeable protcol by default.
Let me know if this helps.
