The remote host is missing an update to smail announced via advisory DSA 722-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20722-1

A buffer overflow has been discovered in Smail, an electronic mail transport system, which allows remote attackers and local users to execute arbitrary code. For the stable distribution (woody) this problem has been fixed in version 3.2.0.114-4woody1. For the unstable distribution (sid) this problem has been fixed in version 3.2.0.115-7. We recommend that you upgrade your smail package.