邮箱服务器网络异常，日志中有大量异常IP登陆信息，求看看

Jul 1 16:41:54 air postfix/smtpd[10160]: warning: unknown[223.240.70.215]: SASL LOGIN authentication failed: authentication failure
Jul 1 16:41:54 air postfix/smtpd[10160]: lost connection after AUTH from unknown[223.240.70.215]
Jul 1 16:41:54 air postfix/smtpd[10160]: disconnect from unknown[223.240.70.215]
Jul 1 16:41:55 air postfix/smtpd[10160]: connect from unknown[223.240.70.215]
Jul 1 16:41:56 air postfix/smtpd[10160]: warning: unknown[223.240.70.215]: SASL LOGIN authentication failed: authentication failure
Jul 1 16:41:56 air postfix/smtpd[10160]: lost connection after AUTH from unknown[223.240.70.215]
Jul 1 16:41:56 air postfix/smtpd[10160]: disconnect from unknown[223.240.70.215]
Jul 1 16:41:56 air postfix/smtpd[10160]: connect from unknown[223.240.70.215]
Jul 1 16:41:57 air postfix/smtpd[10160]: warning: unknown[223.240.70.215]: SASL LOGIN authentication failed: authentication failure
Jul 1 16:41:57 air postfix/smtpd[10160]: lost connection after AUTH from unknown[223.240.70.215]
Jul 1 16:41:57 air postfix/smtpd[10160]: disconnect from unknown[223.240.70.215]

最近邮箱服务器报警流量异常，查了一下对应时间点的maillog都是这个
因为之前有被利用发垃圾邮件，所以加过黑名单和修改过部分用户密码，不知道现在这个是不是别人又在攻击，还有就是这个尝试连接会印象网络流量么，哪位大神求分析一下。

还是很多垃圾邮件的服务器不断的试图访问，建议po主更换邮件服务器的端口，我之前发生的情况和你一样，更换端口后就完全好了