postfix: add fsmpi smtp mynetworks exception

postfix/templates/master.cf.j2

@@ -23,6 +23,9 @@ dnsblog   unix  -       -       y       -       0       dnsblog
 tlsproxy  unix  -       -       y       -       0       tlsproxy
 {% else %}
 smtp     inet  n       -       y       -       -       smtpd
+{% if postfix_fsmpi|default(false) %}
+  -o smtpd_sender_restrictions=permit_mynetworks,reject_sender_login_mismatch
+{% endif %}
 {% endif %}
 {% if postfix_enable_submission %}
 submission inet n       -       y       -       -       smtpd