Buffer overflow in XMail POP3 server before version 0.59 allows remote attackers to execute arbitrary commands via a long APOP command.
https://exchange.xforce.ibmcloud.com/vulnerabilities/5191
https://euvd.enisa.europa.eu/vulnerability/EUVD-2000-0828
http://www.securityfocus.com/bid/1652
http://archives.neohapsis.com/archives/bugtraq/2000-09/0001.html