The remote host is vulnerable to a buffer overflow.
The remote client is running Sylpheed, an email client for Unix and Unix-like operating systems. This version is vulnerable to a buffer overflow via specially crafted MIME messages or attachments. An attacker exploiting this flaw would need to be able to convince a user to open a malicious email message. Successful exploitation would lead to a Denial of Service or remote code execution.
Upgrade to version 1.0.4, 1.9.5 or higher.