如何禁止这些ip地址？

Question

tail /var/log/maillog
Oct 30 09:28:44 localhost postfix/smtpd[3226]: disconnect from unknown[103.252.50.140]
Oct 30 09:30:47 localhost postfix/smtpd[3230]: connect from unknown[191.96.249.63]
Oct 30 09:30:48 localhost postfix/smtpd[3230]: warning: unknown[191.96.249.63]: SASL LOGIN authentication failed: authentication failure
Oct 30 09:30:48 localhost postfix/smtpd[3230]: disconnect from unknown[191.96.249.63]
Oct 30 09:31:12 localhost postfix/smtpd[3230]: connect from unknown[191.96.249.70]
Oct 30 09:31:13 localhost postfix/smtpd[3230]: warning: unknown[191.96.249.70]: SASL LOGIN authentication failed: authentication failure

请问，我使用iptable来禁止这些ip 地址，还是，设置dovecot的黑名单来禁止它们？