Unspecified vulnerability in the IMAP server in hMailServer 4.4.1 allows remote authenticated users to cause a denial of service (resource exhaustion or daemon crash) via a long series of IMAP commands.
https://exchange.xforce.ibmcloud.com/vulnerabilities/44429
http://www.securityfocus.com/archive/1/495361/100/0/threaded
http://www.hmailserver.com/documentation/?page=changelog