Postfix – SMTPS and Submission Confusion Explained

You need to uncomment the smtps line in your /etc/postfix/master.cf

What you've current got looks like the following. Try uncommenting the first two lines and restarting Postfix. You should see that Postfix is now listening on port 465. You may also need to open that port on your firewall.

#smtps     inet  n       -       n       -       -       smtpd
#  -o smtpd_tls_wrappermode=yes
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING

It's simply a clean way of overriding main.cf since usually smtpd_client_restrictions in main.cf isn't used, which is the same as saying by default it is set to smtpd_client_restrictions = permit.

You could achieve the same result by overriding smtpd_recipient_restrictions as you say in your question, in which case you wouldn't need the smtpd_client_restrictions statement, perhaps that might have an unnoticeable performance benefit but if there were other restrictions present in smtpd_recipient_restrictions in main.cf relevant to authenticated clients you would also have to add them to master.cf too and remember to keep them in sync with future edits.

Also from the debian packagers point of view, overriding smtpd_client_restrictions is a safer bet since it's much less likely it was doing anything in main.cf compared with smtpd_recipient_restrictions.