I just setup 2 postfix hidden services and tried to send email using this method.  It didn't work.  I can telnet to each server and they seem to be up.  However the command substitution smtp_tor is not working. Postfix gives the error:

warning: process /usr/lib/postfix/bin/smtp_tor pid 5513 exit status 1
warning: /usr/lib/postfix/bin/smtp_tor: bad command startup -- throttling

However it works when sending mail to yourself on the same server.  I think it is having a name resolution problem. Any ideas on how to fix this?