在系统日志文件（debian）中我有上千行类似以下内容：
Dec 3 10:38:59 vps277777 postfix/smtpd[593]: warning: connect to Milter service inet:localhost:12301: Connection refused
Dec 3 10:39:00 vps277777 postfix/smtpd[593]: lost connection after AUTH from unknown[185.234.216.87]
Dec 3 10:39:00 vps277777 postfix/smtpd[593]: disconnect from unknown[185.234.216.87] ehlo=1 auth=0/1 commands=1/2
Dec 3 10:39:00 vps277777 postfix/smtpd[593]: connect from unknown[185.234.216.87]
Dec 3 14:28:31 vps277777 postfix/anvil[6292]: statistics: max connection rate 1/60s for (smtp:27.100.26.165) at Dec 3 14:22:10
Dec 3 14:28:31 vps277777 postfix/anvil[6292]: statistics: max connection count 1 for (smtp:27.100.26.165) at Dec 3 14:22:10
Dec 3 14:28:31 vps277777 postfix/anvil[6292]: statistics: max cache size 1 at Dec 3 14:22:10
每天。
我的服务器从未用于接收电子邮件。因此，应该没有来自外部的连接。如何阻止所有内容？