RPM of the new version of Mozilla Foundation messaging client is available in remi for fedora ≤ 12 (backport of F-14 version).
Start by reading : Thunderbird Release Notes As always: yum --enablerepo=remi update thunderbird enigmail (version 1.1.2) and lightning (version 1.0b3pre) extensions are also available. RPM are availalble for fedora 10 to 12.... Lire thunderbird-3.1.6