/var/log/maillog會記錄包含系統上運行的郵件服務器的日志信息，比如記錄 postfix 或 sendmail 運行時的日志信息
[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
可以分為幾個字段來描述這些事件信息：
1. 事件的日期和時間
2. 事件的來源主機
3. 產生這個事件的程序[進程號]
4. 實際的日志信息