Upgrade to version 9.61 or higher, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.
Vendor Specific News/Changelog Entry: http://files.altn.com/MDaemon/Release/RelNotes_en.txt
Security Tracker: 1018342
Secunia Advisory ID:25968
ISS X-Force ID: 35285
Bugtraq ID: 24787