The remote host is vulnerable to an arbitrary 'command insertion' flaw.
The remote host is running SpamAssassin, an anti-spam software application that detects and blocks spam emails. Due to a content-parsing error, SpamAssassin can be tricked into executing arbitrary commands with the privileges of the SpamAssassin spamd process. Additionally, the remote version of SpamAssassin must be running with either '--vpopmail' or '--paranoid' enabled.
Upgrade or patch according to vendor recommendations.