Microsoft Commercial Internet System (MCIS) IMAP server allows remote attackers to cause a denial of service via a malformed IMAP request.
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2000/ms00-001
http://www.securityfocus.com/bid/912
http://support.microsoft.com/default.aspx?scid=kb%3B%5BLN%5D%3BQ246731