The remote host is missing an update to sylpheed announced via advisory DSA 906-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20906-1

Colin Leroy discovered several buffer overflows in a number of importer routines in sylpheed, a light-weight e-mail client with GTK+, that could lead to the execution of arbitrary code. The following matrix explains which versions fix this vulnerability old stable (woody) stable (sarge) unstable (sid) sylpheed 0.7.4-4woody1 1.0.4-1sarge1 2.0.4-1 sylpheed-gtk1 n/a n/a 1.0.6-1 sylpheed-claws 0.7.4claws-3woody1 1.0.4-1sarge1 1.0.5-2 sylpheed-claws-gtk2 n/a n/a 1.9.100-1 We recommend that you upgrade your sylpheed package.