Problem with Postscreen

[Rod K]

I am receiving the following message when testing (not enabled) postscreen:
 smtp postfix/postscreen[1516]: warning: cannot connect to service 
private/smtpd: No such file or directory

The following are my main.cf entries:

smtp           pass    -       -       -       -       -       smtpd
        -o receive_override_options=no_address_mappings
smtp           inet    n       -       n       -       1       postscreen
tlsproxy      unix    -       -       n       -       0       tlsproxy
dnsblog     unix    -       -       n       -       0       dnsblog

Any ideas?