The thunderbird-3.0-2.5.b3 package install this new version over the version 2 (and remove the thunderbird3 if installed)

WARNING : a backup of your profile (.thunderbird directory) seems mandatory.

Start by reading :

As always :

yum --enablerepo=remi update thunderbird

The enigmail extension is also available.

Actually the lightning extension is not compatible (I work on it) and will be disabled.

I use the beta 2 for some time without any problem, it's the reason why I don't want to maintain the version 2.0 in my repository.

Build for Fedora 8 to 10 are available (other will, perhaps, come in a few days).