A brief example:
/etc/postfix/sender_access:
example.com reject Sender address requires authentication
other.example reject Sender address requires authentication
Do "postmap /etc/postfix/sender_access", then add this to main.cf:
smtpd_sender_restrictions =
permit_mynetworks
permit_sasl_authenticated
check_sender_access hash:/etc/postfix/sender_access
With this, only senders in a trusted network, or authenticated
senders, can do "MAIL FROM:<u...@example.com>" etc.
This does not restrict the address in the From: message header.
Wietse
