Enigmail

Enigmail is a Thunderbird security extension, enabling you to write and receive email messages signed and/or encrypted with GnuPG/OpenPGP.

Simply install the following package(s):

• enigmail (main)

Additionally, you need a running GnuPG to write and receive signed and/or encrypted emails.

The package manager installs the Add-on into /usr/lib/mozilla instead of your profile's extensions dir. This has some advantages because Enigmail is platform depended.¹⁾ So if you want to share/sync your Thunderbird profile e.g. between a 32bit and 64bit Ubuntu, everything is fine if you are using the package manager on all machines. If you used the common .xpi (which installs Enigmal into <your-profile-dir>/extensions), you would have problems at one of the machines.
And don't worry about the settings: all versions are using the profile files prefs.js and pgprules.xml to store them, so your settings and Per-Recipient rules will be in sync.

You can use the default installation method if you do not plan to use your profile on different platforms, though. Go to the download page and get the fitting version for your environment. Do not use the Mozilla Add-on page because it is not able to detect the correct platform in every case which may leads to offering you an incompatible Enigmail version.

Simply use the default installation method. See https://addons.mozilla.org/thunderbird/addon/71 to get the .xpi.

• Offical Project Website
• Thunderbord Mail DE - Enigmail OpenPGP