The remote host is missing an update to mailman announced via advisory DSA 1027-1. A potential denial of service problem has been discovered in mailman, the web-based GNU mailing list manager. The (failing) parsing of messages with malformed mime multiparts sometimes caused the whole mailing list to become inoperative. The old stable distribution (woody) is not vulnerable to this issue.
For the stable distribution (sarge) this problem has been fixed in version 2.1.5-8sarge2. For the unstable distribution (sid) this problem will be fixed soon. We recommend that you upgrade your mailman package. https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201027-1