The remote host is missing an update to xemacs21 announced via advisory DSA 671-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20671-1

Max Vozeler discovered several format string vulnerabilities in the movemail utility of Emacs, the well-known editor. Via connecting to a malicious POP server an attacker can execute arbitrary code under the privileges of group mail. For the stable distribution (woody) these problems have been fixed in version 21.4.6-8woody2. For the unstable distribution (sid) these problems have been fixed in version 21.4.16-2. We recommend that you upgrade your emacs packages.