Precise Pangolin (12.04) is a LTS (Long Term Support) release of Ubuntu. Why is Thunderbird 11 included, instead of Thunderbird 10 ESR (Extended Support Release)?
Is there any way to install Thunderbird 10 ESR on Ubuntu 12.04?
Because we use Firefox 11 instead of ESR and most of the same reasons apply to Thunderbird as Firefox for using the rapid release version. The decision to not use ESR by default in the LTS was surprising to me, so I asked on the mailinglists (you can find the thread here: https://lists.ubuntu.com/archives/ubuntu-desktop/2012-February/003672.html) and Jason Warner from Canonical answered:
Firefox adopted a rapid release model for various reasons, but among them was that they needed the browser to keep up with the pace of innovation on the internet. Ubuntu needs to be out in front of these things and be pushing the very edge of what is possible, particularly in the browser. I do not think we can ship a browser that will lag by 12 months in any sense; the risks too far outweigh the rewards.
Anyway, you'd like to install Thunderbird ESR, you can donwload it here: http://mozilla.org/en-US/thunderbird/organizations/all-esr.html
You simply need to extract it into your home folder and add a script called
every time your user calls thunderbird
You can also see this blog post from Chris Coulson on why the ESR was not selected.