The remote host is missing an update to exim4 announced via advisory DSA 2566-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202566-1

It was discovered that Exim, a mail transport agent, is not properly handling the decoding of DNS records for DKIM. Specifically, crafted records can yield to a heap-based buffer overflow. An attacker can exploit this flaw to execute arbitrary code. For the stable distribution (squeeze), this problem has been fixed in version 4.72-6+squeeze3. For the testing distribution (wheezy), this problem has been fixed in version 4.80-5.1. For the unstable distribution (sid), this problem has been fixed in version 4.80-5.1. We recommend that you upgrade your exim4 packages.