Buffer overflow in the NetWin DSMTP 2.7q in the NetWin dmail package allows remote attackers to execute arbitrary commands via a long ETRN request.
https://exchange.xforce.ibmcloud.com/vulnerabilities/4579
http://netwinsite.com/dmail/security.htm
http://archives.neohapsis.com/archives/bugtraq/2000-05/0407.html