MailEnable smtpd contains a bug where unicoded values transmitted in the EHLO command are interpreted as memory addresses. This leads to a Denial of Service condition.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/37024/mailenable_ehlo_dos.txt
Source: https://packetstormsecurity.com/files/37024/mailenable_ehlo_dos.txt.html