The remote host is missing an update to mutt announced via advisory DSA 268-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20268-1

Core Security Technologies discovered a buffer overflow in the IMAP code of Mutt, a text-oriented mail reader supporting IMAP, MIME, GPG, PGP and threading. This problem allows a remote malicious IMAP server to cause a denial of service (crash) and possibly execute arbitrary code via a specially crafted mail folder. For the stable distribution (woody) this problem has been fixed in version 1.3.28-2.1. The old stable distribution (potato) is not affected by this problem. For the unstable distribution (sid) this problem has been fixed in version 1.5.4-1. We recommend that you upgrade your mutt package.