Buffer overflow in Internet Mail Service (IMS) for Microsoft Exchange 5.5 and 5.0 allows remote attackers to conduct a denial of service via AUTH or AUTHINFO commands.
https://exchange.xforce.ibmcloud.com/vulnerabilities/1223
http://xforce.iss.net/alerts/advise4.php
http://www.ciac.org/ciac/bulletins/i-080.shtml
http://support.microsoft.com/default.aspx?scid=kb%3B%5BLN%5D%3BQ169174