The remote host is missing an update to postgrey announced via advisory DSA 1121-1. Peter Bieringer discovered that postgrey, an greylisting implementation for Postfix, is vulnerable to a format string attack that allows remote attackers to the daemon.
For the stable distribution (sarge) this problem has also been fixed in version 1.21-1volatile4 in the volatile archive. For the unstable distribution (sid) this problem has been fixed in version 1.22-1. We recommend that you upgrade your postgrey package. https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201121-1