First, go to the downloads page, right-click the link for the “Mozilla Firefox/Mozilla Thunderbird” extension link, and click “Save Link As…” Save the extension somewhere on your computer easy to find. In Thunderbird, push Alt to show the menu options at the top of the window, click “Tools,” and then click “Add-ons.” Next, click the gear icon to bring up the extensions menu:
Click “Install Add-on From File…” and select the extension that you downloaded. You’ll get a window confirming that you want to install the add-on. Click “Install.” Restart Thunderbird when prompted to do so. Now, push Alt to show the menu options at the top of the window, and then click “Tools,” and and look for the “enMailing Options” item:
Click that menu item, and the following dialog will pop up:
Enter your enMailing username and password. Also specify a name for this device. It’s a good idea to use a name that you will be able to recognize in the future, such as “Thunderbird (home)” or “Thunderbird (work).” Giving a descriptive name will make it easier for you to de-authorize the device in the future should you ever want to. After entering your username, password, and the device name, click “Authorize.” If your username and password were correct, Thunderbird will become an authorized device:
Ignore the fact that the device name is “FIrefox (home).” I’m just reusing the image from the Firefox guide.
The “Default Group for Encrypting” setting allows you to set the group for which you will encrypt messages. This is easy to change later, but you can change it now if you want to. Click “OK.” You are now ready to encrypt and decrypt messages. In the compose message window, you will notice some new toolbar items:
The first button is a toggle that tells Thunderbird whether to encrypt your entire message before sending. The second button allows you to select the group for which to encrypt the message. The third button allows you to decrypt your message if you’ve partially encrypted it. The fourth option opens the enMailing settings window.
To encrypt your entire message, just toggle the “Encrypt on Send” button, type your message, and send away. If you want to see the entire message encrypted, you can right-click the message body and select “Encrypt All.” To decrypt and continue editing, click the “Decrypt” toolbar button.
To encrypt part of your message, select the text you want to encrypt, right-click, and select “Encrypt Selection.”
Keep in mind that all encryption is done for the currently selected group. If you select one group, encrypt a portion of your message, select a different group, and then encrypt a different portion of your message, those parts of your message will be encrypted for each different group.
Reading encrypted messages that you receive is automated. Any encrypted messages are automatically displayed decrypted in the reading pane. If you open a message in its own window, it will likewise automatically be decrypted. When you reply to a message that has encryptions, the message will be decrypted in your compose window. Additionally, the “Encrypt on Send” option will be automatically toggled on.