The remote host is missing an update to icedove announced via advisory DSA 2556-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202556-1

Several vulnerabilities were discovered in Icedove, Debian's version of the Mozilla Thunderbird mail and news client. This includes several instances of use-after-free and buffer overflow issues. The reported vulnerabilities could lead to the execution of arbitrary code, and additionally to the bypass of content-loading restrictions via the location object. For the stable distribution (squeeze), this problem has been fixed in version 3.0.11-1+squeeze13. For the testing distribution (wheezy), this problem has been fixed in version 10.0.7-1. For the unstable distribution (sid), this problem has been fixed in version 10.0.7-1. We recommend that you upgrade your icedove packages.