LinuxBasics.org

• Install Enigmail via extensions or package manager.
  • You must have Gnu Privacy Guard installed on your system. Check your package manager to make sure you do. The package name is probably gnupg or a derivative of that.
  • Get Enigmail: https://addons.mozilla.org/thunderbird/71/ (Note the directions right under “Install Now”) or it might be available by sudo apt-get install mozilla-thunderbird-enigmail on Debian-type systems like Ubuntu.
  • If you followed the above instruction, you will have the .xpi file somewhere handy. Open Thunderbird and go to Tools and then Extensions. Click “Install” at the bottom left. Then navigate to where you have saved the .xpi file and choose it. That will install Enigmail after you close and reopen Thunderbird.
• Generate and upload key
  • If you have never generated a key for the email account you want to use, you can do that right from Enigmail with theEnigmail OpenPGP Key Manager.
    • Go to OpenPGP in the Thunderbird menu and then Key Management.
    • Click on Generate/New Key Pair. Make sure the proper account is showing in the drop down menu at the top of the window and type in your passphrase twice. The defaults for the other things are probably fine. You can increase or decrease the key size and change the expiration time.
    • Upload your key. In the menu choose OpenPGP/Key Management. Highlight the key/s you want to upload and choose Keyserver/Upload Public Keys. Eventually it will get propogated to other keyservers besides the one you use. It can take weeks for this to happen; so don’t be surprised when people can’t find your key right away. Those using Enigmail will probably use the same keyserver as you do; so they will find your public key right away.
• Configure Enigmail general preferences and those for your email account/s
  • Set up your OpenPGP preferences for your email account. Right click on the account name in the folder panel and choose Properties. In that block choose “OpenPGP Security”.
    • Check “Enable OpenPGP Support for this account” and check one of the two blocks for how your key gets selected, either by the account name or by your specific choice of keys. Choose whether you want to sign and/or encrypt by default for this account.
    • Choose your Preferences in OpenPGP in the Thunderbird menu under Preferences.
      • Idle time can be change to suit your tastes
      • Keyservers are probably pretty good on a fresh install of Enigmail
      • Under PGP/Mime, I would recommend alway use PGP/Mime unless you find that is causes problems. This means that the text used for signing will not be visible ordinarily. It makes a lot of folks happier to have it that way, but can cause problems where those little attachments it uses are not accepted. PGP/Mime is pretty much preferred.
• Sign your mail - or encrypt when you need it
  • Send an email. If you have not set signing by default, you need to Choose to sign it in the OpenPGP menu on your editing window prior to sending.
  • Enter your passphrase to allow the signed email to be sent. You will have your earlier specified number of minutes to send another email without entering your passphrase.
• Verify or decrypt incoming email. It will just happen if “Automatically Decrypt/Verify Messages” is checked in the OpenPGP menu. You may see that a message is unverified. There will be a pen on the email at the top. Click on that to attempt to download the public key for that email address. If it is available, the email should verify.

More:

• Be sure to generate a revocation certificate and save it in a safe place in case you need to revoke a key someday and no longer have your private key available on your computer. That feature is also in the Key Management.
• Enigmail help information: http://enigmail.mozdev.org/help.html
• GPG Keyservers

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