root # emerge -av postfix
  # 修改配置文件
  # /etc/postfix/main.cf : myhostname,  myorigin,  inet_interfaces,  mydestination,  mynetworks,  relay_domains,  alias_maps,  alias_database
  # /etc/mail/aliases    : root : root,tim
  # /etc/postfix/access  : 允许/不允许通过的IP地址
  root # vim /etc/postfix/main.cf
  root # vim /etc/mail/aliases
  root # echo "192.168.0.100  OK" >> /etc/postfix/access
  root # echo "192.168.0.101  OK" >> /etc/postfix/access
  root # echo "xxx.com  REJECT" >> /etc/postfix/access
  #检查配置
  root # postfix check
  #转换档案的资料库
  root # postmap hash:/etc/postfix/access
  root # postalias hash:/etc/mail/aliases
  #启动服务
  root # /etc/init.d/postfix start
  #开机启动
  root # rc-update add postfix default

  #修改了部分配置
  myhostname = tiimmm.com
  myorigin = $myhostname
  # inet_interfaces = $myhostname, localhost
  inet_interfaces = all
  mydestination = $myhostname, localhost, tiimmm.com
  mynetworks = 127.0.0.0/8, 192.168.0.0/24, 192.168.122.0/24, hash:/etc/postfix/access
  relay_domains = $mydestination
  alias_maps = hash:/etc/mail/aliases
  alias_database = hash:/etc/mail/aliases

  #修改了部分配置
  root : root,tim