Qpopper 2.53 and 3.0 does not properly identify the \n string which identifies the end of message text, which allows a remote attacker to cause a denial of service or corrupt mailboxes via a message line that is 1023 characters long and ends in \n.
http://www.securityfocus.com/templates/archive.pike?list=1&msg=9763.000421%40SECURITY.NNOV.RU