Courier SqWebMail File Disclosure Vulnerability Solution:
Debian has released an advisory. Information about obtaining and applying fixes are available in the referenced advisory.
Gentoo has released a security advisory for this issue. Gentoo users are advised to issue the following commands to update their systems:
emerge rsync
emerge courier
emerge clean
See the referenced advisory for more details.
Double Precision Incorporated Courier MTA 0.37.3