Please include this in the postfix lua together with a fix for graylisting under Ubuntu. I don't know the correct implemantation. I tried this:
smtpd_sender_restrictions =
permit_mynetworks,
reject_authenticated_sender_login_mismatch,
reject_unknown_address,
reject_unknown_sender_domain,
reject_non_fqdn_sender,
check_sender_access hash:/etc/postfix/sender_access
But then I could not send at all any more. Please give this a higher priority, because it helps to identify a spamming mail account, a continuous problem with hosters.