The remote host is missing an update to the system as announced in the referenced advisory.

Update your system with the appropriate patches or software upgrades. https://www.isc.org/software/inn/2.5.3article http://www.vuxml.org/freebsd/a7975581-ee26-11e1-8bd8-0022156e8794.html

The following package is affected: inn CVE-2011-0411 The STARTTLS implementation in Postfix 2.4.x before 2.4.16, 2.5.x before 2.5.12, 2.6.x before 2.6.9, and 2.7.x before 2.7.3 does not properly restrict I/O buffering, which allows man-in-the-middle attackers to insert commands into encrypted SMTP sessions by sending a cleartext command that is processed after TLS is in place, related to a 'plaintext command injection' attack.