The remote host is missing an update to postfix announced via advisory DSA 363-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20363-1

The postfix mail transport agent in Debian 3.0 contains two vulnerabilities: CVE-2003-0468: Postfix would allow an attacker to bounce-scan private networks or use the daemon as a DDoS tool by forcing the daemon to connect to an arbitrary service at an arbitrary IP address and either receiving a bounce message or observing queue operations to infer the status of the delivery attempt. CVE-2003-0540: a malformed envelope address can 1) cause the queue manager to lock up until an entry is removed from the queue and 2) lock up the smtp listener leading to a denial of service For the current stable distribution (woody) these problems have been fixed in version 1.1.11-0.woody3. For the unstable distribution (sid) these problems will be fixed soon. We recommend that you update your postfix package.