A high scalable E-mail system is presented to overcome the shortage of traditional E-mail system. Using this technology, the system can be flexibly upgraded and the original architecture and performance will not be affected. The LDAP user management strategy, system architecture and the work principle are illustrated. The methods of system implementation by QMAIL and QMAIL-LDAP are introduced. A test environment is set up and can see great performance of the system through the obtained running data.