source: https://www.securityfocus.com/bid/26856/info QK SMTP Server is prone to multiple remote denial-of-service vulnerabilities that occur when handling malformed SMTP commands. An attacker can exploit these issues to crash the affected application, denying service to legitimate users. These issues affects QK SMTP Server 3; other versions may also be affected. HELO ../A/ * 950 MAIL FROM: ../A/ * 950 RCPT TO: ../A/ * 950 data ../A/ * 950