First let me explain my setup. I'm using postfix 2.9.6 on Debian Wheezy. I do not allow AUTH on port 25, and force MUAs to use a submission service on port 587 instead. Debian comes with the following configuration in master.cf (commented by default):
submission inet n - - - - smtpd -o syslog_name=postfix/submission -o smtpd_tls_security_level=encrypt -o smtpd_sasl_auth_enable=yes -o smtpd_client_restrictions=permit_sasl_authenticated,reject -o milter_macro_daemon_name=ORIGINATING
I do not understand why permit_sasl_authenticated is in smtpd_client_restrictions. To allow relay access it has to also be added to smtpd_recipient_restrictions (or smtpd_relay_restrictions, for postfix >= 2.10), either in main.cf or preferably in an additional override for the submission service in master.cf:
Either way results in checking for authentication twice, and with delayed evaluation of restriction lists, both checks are done at the RCPT TO stage. Without relay access, AUTH clients could send to $mydestination, but the MTA on port 25 already allows that anyway. Without delayed evaluation, the smtpd wouldn't even have information about AUTH yet when it does the client checks.
Is there any benefit at all to having permit_sasl_authenticated in smtpd_client_restrictions, ever? What is the use case for this?