Postfix mta 如何在Postfix中阻止发送给未知接收者的消息

我在Ubuntu上运行Postfix邮件服务器，有时会将垃圾邮件发送到

receiver=

postfix/smtpd[15571]：从a.benient.com[198.144.154.163]连接
postfix/smtpd[15571]：从a.benient.com[198.144.154.163]建立的匿名TLS连接：TLSv1，带密码ECDHE-RSA-AES256-SHA（256/256位）
policyd spf[15576]：预先发送收到的spf:Pass（mailfrom）identity=mailfrom；客户ip=198.144.154.163；helo=a.benient.com；信封=qbccaa@benient.com; 接受者=
postfix/smtpd[15571]：A08363F55C:client=a.benient.com[198.144.154.163]
后缀/清除[15578]：A08363F55C:消息id=
opendkim[690]：A08363F55C:s=benient d=benient.com SSL
后缀/qmgr[24766]：A08363F55C:from=，size=18601，nrcpt=1（队列活动）

如何阻止此类消息

postfix/smtpd[15571]: connect from a.benient.com[198.144.154.163]
postfix/smtpd[15571]: Anonymous TLS connection established from a.benient.com[198.144.154.163]: TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)
policyd-spf[15576]: prepend Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=198.144.154.163; helo=a.benient.com; envelope-from=qbccaa@benient.com; receiver=<UNKNOWN>
postfix/smtpd[15571]: A08363F55C: client=a.benient.com[198.144.154.163]
postfix/cleanup[15578]: A08363F55C: message-id=<F5ABB69D843DC3327E28B32E1F199882@twk>
opendkim[690]: A08363F55C: s=benient d=benient.com SSL
postfix/qmgr[24766]: A08363F55C: from=<qbccaa@benient.com>, size=18601, nrcpt=1 (queue active)