Q:

Allow SMTP AUTH only from mynetworks

Is it possible to allow SMTP AUTH only from IPs in mynetworks? I've tested a bunch of options but no one worked. Here's the actual state of my main.cf:
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = mx1.domain.com
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = mail.domain.com, localhost.domain.com, localhost
relayhost =
mynetworks = 172.20.1.0/24 172.18.1.0/24 192.168.0.0/24 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_command = procmail -a "$EXTENSION"
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
virtual_mailbox_domains = mysql:/etc/postfix/mysql-virtual-mailbox-domains.cf
virtual_mailbox_maps = mysql:/etc/postfix/mysql-virtual-mailbox-maps.cf
virtual_alias_maps = mysql:/etc/postfix/mysql-virtual-alias-maps.cf
virtual_transport = dovecot
dovecot_destination_recipient_limit = 1
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes
smtpd_tls_security_level = may
smtpd_tls_auth_only = no

smtpd_recipient_restrictions = 
    check_recipient_access mysql:/etc/postfix/blocked-recipients.cf,
    permit_mynetworks,
    permit_sasl_authenticated,
    reject_unauth_destination,
    check_sender_access hash:/etc/postfix/sender_access

message_size_limit = 409600000

A:

You'll likely want to use smtpd_sasl_exceptions_networks.

A:

Thanks @84104. Your answer led me to find this topic which solved my problem.

smtpd_sasl_exceptions_networks does not announce AUTH support but still allows AUTH from any IP.
This feature was donated to prevent certain network clients from
  messing  up when the server announces AUTH support but the client has
  no  login information. With smtpd_sasl_exceptions_networks, those
  clients  would not try to authenticate and all was well.
smtpd_sasl_exceptions_networks is obsoleted by
  smtpd_discard_ehlo_keywords  and
  smtpd_discard_ehlo_keyword_address_maps. The latter two prevent 
  Postfix from accepting AUTH commands. 
smtpd_sasl_exceptions_networks should probably be deprecated and
  eventually removed from documentation.

