IMAP server in Alt-N Technologies MDaemon 3.5.6 allows a local user to cause a denial of service (hang) via long (1) SELECT or (2) EXAMINE commands.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6279
https://euvd.enisa.europa.eu/vulnerability/EUVD-2001-0576
http://www.securityfocus.com/bid/2508
http://archives.neohapsis.com/archives/bugtraq/2001-03/0365.html