The remote host is missing an update to perdition announced via advisory DSA 1398-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201398-1

Bernhard Mueller of SEC Consult has discovered a format string vulnerability in perdition, an IMAP proxy. This vulnerabilty could allow an unauthenticated remote user to run arbitrary code on the perdition server by providing a specially formatted IMAP tag. For the stable distribution (etch), this problem has been fixed in version 1.17-7etch1 For the old stable distribution (sarge), this problem has been fixed in version 1.15-5sarge1 We recommend that you upgrade your perdition package.