The remote host is missing an update to php-mail announced via advisory DSA 1938-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201938-1

It was discovered that php-mail, a PHP PEAR module for sending email, has insufficient input sanitising, which might be used to obtain sensitive data from the system that uses php-mail. For the stable distribution (lenny), this problem has been fixed in version 1.1.14-1+lenny1. For the oldstable distribution (etch), this problem has been fixed in version 1.1.6-2+etch1. For the testing distribution (squeeze), this problem will be fixed soon. For the unstable distribution (sid), this problem has been fixed in version 1.1.14-2. We recommend that you upgrade your php-mail packages.