Microsoft Windows SMTP Server MX Record Denial of Service Vulnerability

Summary
The Microsoft Windows Simple Mail Transfer Protocol (SMTP) Server is prone to a denial-of-service vulnerability and to to an information-disclosure vulnerability. Successful exploits of the denial-of-service vulnerability will cause the affected SMTP server to stop responding, denying service to legitimate users. Attackers can exploit the information-disclosure issue to gain access to sensitive information. Any information obtained may lead to further attacks.
Solution
Microsoft released fixes to address this issue. Please see the references for more information.
References