Yawebmail 源码，一个网页邮件收发系统-Yawebmail is a Web-(Online-)Application that enables you to establish a SMTP-, POP3- or IMAP-Connection, even if you are behind a firewall that prevents Mail-Communication- you only need to have HTTP-Access to the Internet.

功能简单的防火墙，但对于编程设计有借鉴意义，供大家参考-Simple function of firewalls, but designed for programming reference for your reference