source: https://www.securityfocus.com/bid/30605/info

NoticeWare Email Server NG is prone to a denial-of-service vulnerability because it fails to handle user-supplied input.

Remote attackers can exploit this issue to deny service to legitimate users.

NoticeWare Email Server NG 4.6.2 and 4.6.3 are vulnerable; other versions may also be affected. 

The following exploit example is available:

A001 LOGIN Ax5000 AAAAA