Restriction classes should do it - it's a very specific application of what was designed as a general method. The authorisation is based on the sender SMTP envelope address, so it can be spoofed.
Put in /etc/postfix/main.cf:
Code:
smtpd_recipient_restrictions =
check_recipient_access hash:/etc/postfix/protected_destinations
...the usual stuff...
smtpd_restriction_classes = authorised_senders
authorised_senders = check_sender_access hash:/etc/postfix/OK_senders, reject
Put in /etc/postfix/protected_destinations:
Code:
y@y.com authorised_senders
Put in /etc/postfix/OK_senders:
Code:
some@domain.com OK