Finding the "nearest" site is also complicated by the fact that the
 host you find might route mail in ways you wouldn't expect.  That is,
 even if you can reach BITBOX.XYZ.EDU on the Internet, it might not
 send mail back to you directly.  If they are a Bitnet host, and haven't
 taken steps to handle their own Internet gatewaying, the responses to
 your e-mail could be routed through an INTERBIT gateway.  So, if you
 still want to figure this out, you'll need to examine the path the
 return mail takes on the way back to you as well.  Check the "Received:"
 header lines to see if some gateway gets stuck handling all the mail
 from the host you chose.
 
 -jj