RPM of the new version of Mozilla Foundation messaging client is available in remi for fedora ≤ 14 and enterprise linux 6 (RHEL, CentOS, ...). This is a backport of F-16 version.
Start by reading : Thunderbird Release Notes As always: yum --enablerepo=remi update thunderbird\* enigmail (version 1.3.4) extension are also available. lightning is not yet available because of issue with some incomplete langpacks. RPM of version 9.0 are availalble for fedora 13 and 14, and for enterprise linux 6.... Lire Thunderbird 9