邮件服务器日志：/var/log/maillog

/var/log/maillog会记录包含系统上运行的邮件服务器的日志信息，比如记录 postfix 或 sendmail 运行时的日志信息

[root@localhost ~]# tail /var/log/maillog    
Dec 18 04:00:05 localhost postfix/sendmail[2670]: warning: valid_hostname: numeric hostname: 231.133.13
Dec 18 04:00:05 localhost postfix/sendmail[2670]: fatal: file /etc/postfix/main.cf: parameter mydomain: bad parameter value: 231.133.13
Dec 19 04:00:06 localhost postfix/sendmail[9331]: warning: inet_protocols: IPv6 support is disabled: Address family not supported by protocol
Dec 19 04:00:06 localhost postfix/sendmail[9331]: warning: inet_protocols: configuring for IPv4 support only
Dec 19 04:00:06 localhost postfix/sendmail[9331]: warning: valid_hostname: numeric hostname: 231.133.13

可以分为几个字段来描述这些事件信息：

　　1. 事件的日期和时间
　　2. 事件的来源主机
　　3. 产生这个事件的程序[进程号] 
　　4. 实际的日志信息