The remote host is missing an update to mutt announced via advisory DSA 274-2.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20274-2

Byrial Jensen discovered a couple of off-by-one buffer overflow in the IMAP code of Mutt, a text-oriented mail reader supporting IMAP, MIME, GPG, PGP and threading. This problem could potentially allow a remote malicious IMAP server to cause a denial of service (crash) and possibly execute arbitrary code via a specially crafted mail folder. This advisory only covers the old stable distribution (potato) since DSA 274-1 already fixed the stable distribution (woody). For the old stable distribution (potato) this problem has been fixed in version 1.2.5-5.2. We recommend that you upgrade your mutt package.