The remote host is missing an update to icedove announced via advisory DSA 1830-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201830-1

Several remote vulnerabilities have been discovered in the Icedove mail client, an unbranded version of the Thunderbird mail client. For details on the issues addressed with this update, please visit the referenced security advisories. For the stable distribution (lenny), these problems have been fixed in version 2.0.0.22-0lenny1. As indicated in the Etch release notes, security support for the Mozilla products in the oldstable distribution needed to be stopped before the end of the regular Etch security maintenance life cycle. You are strongly encouraged to upgrade to stable or switch to a still supported mail client. For the testing (squeeze) distribution these problems will be fixed soon. For the unstable distribution (sid), these problems have been fixed in version 2.0.0.22-1. We recommend that you upgrade your icedove packages.