Heap-based buffer overflow in the SvrAppendReceivedChunk function in xlsasink.dll in the SMTP service of Exchange Server 2000 and 2003 allows remote attackers to execute arbitrary code via a crafted X-LINK2STATE extended verb request to the SMTP port.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A4032
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2005/ms05-021
http://www.us-cert.gov/cas/techalerts/TA05-102A.html
http://www.kb.cert.org/vuls/id/275193