As this is a new major version, a backup of your profiles seems mandatory (.thunderbird folder)

Start by reading :

As always:

yum --enablerepo=remi update thunderbird

enigmail (version 1.1.2) and lightning (version 1.0b2pre) extensions are also available.

A annoying issue with this version requires to register extensions on each startup. This should be noticeable .

RPM are availalble for fedora ≥ 8 (older fedora versions should come, or not...). This version will also be available in updates-testing for F-13 (which seems unusual..) but without the workaround for extension issue.