Thunderbird and Postbox: Enigmail

Install the addon (Thunderbird)

Install the Enigmail OpenPGP Thunderbird Addon through the regular Addon manager.

Install the addon (Postbox)

• Download the Enigmail Addon for Postbox
• In Postbox choose Tools > Addons
• Click the gearwheel and then "Install Add-on from File" and select the downloaded package from your disk.
• Restart Postbox

Configure the addon

• You have new menu item OpenPGP. Open it and select "Key Management"
• With the Key Management window open you have menu options to Import Keys (File > Import Keys from File) or generate a new keypair.
• When you want to generate a keypair, be sure to take a look at the "Advanced" Tab to set the Key size to 4096 if you want.
• To activate PGP for your mail account(s) open the Thunderbird (or Postbox) preferences > "Accounts" > Click "OpenPGP Security" beneath your desired mail account > Tick the checkbox to enable OpenPGP.
• I also recommend to check "Use PGP/MIME by default".

Sending encrypted emails

When composing an email you can choose to encrypt and/or sign it using the "OpenPGP" option in the top menu.

When you decided to encrypt your message, it will be encrypted for all recipients once you hit send. When you don't have the public keys of all your recipients you'll get a key management window with the option "Download missing keys".