Summary
The remote host is missing an update as announced
via advisory SSA:2009-232-01.
Solution
https://secure1.securityspace.com/smysecure/catid.html?in=SSA:2009-232-01
Insight
New mozilla-thunderbird packages are available for Slackware 10.2, 11.0, 12.0, 12.1, 12.2, and -current to fix a security issue:
'MFSA 2009-42 Compromise of SSL-protected communication'
More details about the issue may be found here:
http://www.mozilla.org/security/known-vulnerabilities/thunderbird20.html