Outbound auth

[Roman Gelfand]

I have the following smtpd entry in master.cf

smtp      inet  n       -       n       -       -       smtpd
        -o content_filter=lmtp:unix:/tmp/dspam.sock
        -o relay_recipient_maps=hash:/etc/postfix/relay_recipients


What settings would I need to add to requre authentication for
outbound email and no authentication for inbound email?

Thanks in advance