Add support for (local) dovecot auth service.

conf/main_ipv4.conf.sample

@@ -289,6 +289,23 @@ mail_user_ports="$standard_mailuser_ports"
 mail_client_ips=""
 forward_mail_client_ips=""
 
+
+# - Dovecot auth service
+# -
+dovecot_auth_service=false
+
+# - Port listen for dovecot auth requests
+# -
+dovecot_auth_port=44444
+
+# - Client Network(s) allowed to connect to dovecot's auth service
+# -
+# - Example:
+# -    dovecot_auth_allowed_networks="192.68.11.64/27 194.150.169.139"
+# - 
+dovecot_auth_allowed_networks=""
+
+
 # - FTP Server
 # -
 ftp_server_ips=""