The remote host is missing an update to sendmail announced via advisory DSA 1155-1. Frank Sheiness discovered that a MIME conversion routine in sendmail, a powerful, efficient, and scalable mail transport agent, could be tricked by a specially crafted mail to perform an endless recursion.
For the stable distribution (sarge) this problem has been fixed in version 8.13.4-3sarge2. For the unstable distribution (sid) this problem has been fixed in version 8.13.7-1. We recommend that you upgrade your sendmail package. https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201155-1