The remote host is vulnerable to a Denial of Service (DoS) attack.
The remote host is running Kerio MailServer version 6.0.10 or lower. There is a flaw in the remote version of this server that would allow an attacker to cause the application to fail. While the details of the flaw are unknown, it is alledged that an attacker can launch the attack without any credentials and render the target service unavailable.
Upgrade to version 6.1.3 Patch 1 or higher.