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to send a 480 response to prompt for AUTHINFO USER/AUTHINFO PASS 
authentication, or a 450 response for AUTHINFO SIMPLE.  When someone
tries posting to my server, they get a 440 response instead.  Some clients
prompt for authentication, but others like Mozilla just say connection 
refused and never prompt for a password:

   lindsey at example.com|/home/lindsey|[348]> telnet news.hort.net 119
   Trying 64.5.98.30...
   Connected to lorien.mallorn.com (64.5.98.30).
   Escape character is '^]'.
   201 news.hort.net InterNetNews NNRP server INN 2.3.3 ready (no posting).
   post 
   440 Posting not allowed
   authinfo user foo
   381 PASS required
   authinfo pass bar
   281 Ok
   post
   340 Ok, recommended ID <auooko$ci6$1 at lorien.mallorn.com>

Is there something that I can do to trigger a 480 or 450 error code if
the user hasn't authenticated instead of the less helpful 440?

Thanks for any tips on client configs and/or authinfo stuff!

Chris