smail: 'No route to host' problem

[Mike <michaelh@hawaii.edu>]

After upgrading my system to Debian 2.0, my smail can't find its
smart_host through which all non-local email is supposed to be
routed. A typical error message in the log file looks like:

09/12/1998 11:04:01: [m0zHSBI-000BVtC] Deferred TO:linux-counter@uninett.no 
ROUTER:smart_host 
TRANSPORT:smtp ERROR:(ERR148) transport smtp: connect: No route to host

I can ping the smart_host, but if I try to telnet to the smart_host on
the smtp port I get the same 'No route to host' error message. No
such problem arises on port 23.

Local mail is delivered just fine and external mail is received just
fine. So, why can't I route to the smart host. 

Thanks in advance for any pointers. Mike.