The remote host is missing an update to mutt announced via advisory DSA 274-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20274-1

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. For the stable distribution (woody) this problem has been fixed in version 1.3.28-2.2. The old stable distribution (potato) is also affected by this problem and an update will follow. For the unstable distribution (sid) this problem has been fixed in version 1.4.0 and above. We recommend that you upgrade your mutt package.