Debian Security Advisory 1688-2 – The update of courier-authlib in DSA 1688-1 caused a regression with setups that do not use mail addresses for authentification. This update fixes this regression.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/73367/dsa-1688-2.txt
Source: https://packetstormsecurity.com/files/73367/Debian-Linux-Security-Advisory-1688-2.html