I had the same problem on my system 10.04
After modifying the permissions on the /var/run/courier/authdaemon directory the error disappeared
chmod 755 /var/run/courier/authdaemon/
--- the error --- Oct 27 15:02:24 servername postfix/pipe[10665]: B30227076F: to=<email address hidden>, relay=maildrop, delay=0.17, delays=0.08/0.01/0/0.07, dsn=5.1.1, status=bounced (user unknown. Command output: ERR: authdaemon: s_connect() failed: Permission denied Invalid user specified. )
I had the same problem on my system 10.04
After modifying the permissions on the /var/run/ courier/ authdaemon directory the error disappeared
chmod 755 /var/run/ courier/ authdaemon/
--- the error --- pipe[10665] : B30227076F: to=<email address hidden>, relay=maildrop, delay=0.17, delays= 0.08/0. 01/0/0. 07, dsn=5.1.1, status=bounced (user unknown. Command output: ERR: authdaemon: s_connect() failed: Permission denied Invalid user specified. )
Oct 27 15:02:24 servername postfix/