The remote host is missing an update as announced via advisory SSA:2004-043-01.

https://secure1.securityspace.com/smysecure/catid.html?in=SSA:2004-043-01

Mutt is a text-based program for reading electronic mail. New mutt packages are available for Slackware 8.1, 9.0, 9.1, and -current. These have been upgraded to version 1.4.2i to fix a buffer overflow that could lead to a machine compromise. All sites using mutt should upgrade to the new mutt package. More details about this issue may be found in the Common Vulnerabilities and Exposures (CVE) database: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-0078