authpam.c in courier-authdaemon for Courier Mail Server 0.37.3 through 0.52.1, when using pam_tally, does not call the pam_acct_mgmt function to verify that access should be granted, which allows attackers to authenticate to the server using accounts that have been disabled.
https://exchange.xforce.ibmcloud.com/vulnerabilities/23532
http://www.securityfocus.com/bid/15771/
http://www.debian.org/security/2005/dsa-917
http://secunia.com/advisories/17999