If you're looking for some added security for Thunderbird, you might want to look into the various available extensions.
For those that don't use Outlook, Thunderbird is one of the best options for email. Out of the box, Thunderbird is a strong candidate for just about any use. However, if you're looking for some added security for your email client, you might want to look into the many and varied extensions available for the open source email client.
But not every extension is created equal. I have combed through the list of security-related Thunderbird extensions and have found five that are the most useful in creating a significantly more secure email experience. Though not each of these will be usable by everyone, each has its place in the realm of securing your email. Let's dive in and find out which of these apps is suited for you.
Enigmail has been around for a while. This extension allows you to make use of OpenPGP encryption and authentication for your email. Enigmail features automatic encryption/decryption, and key management. The one caveat to this extension is that you must install GnuPG separately (the extension does not do this for you). Enigmail is simple to use; just a click from a drop-down and you can encrypt or decrypt and email. Before using this extension, however, it's best that you have a fundamental understanding of encryption. This extension supports Thunderbird versions 17-19 and can be used on Linux, Mac, and Windows.
2. Abusix Spam Reporter
Abusix Spam Reporter is a simple method of reporting email SPAM to the abusix blackhole.mx system. Once installed, all you have to do is select an email and click the Report Spam button. When you report an email, only the headers of the SPAM email are forwarded. Once reported you can then delete the email or send it to your Junk folder (the extension doesn't handle the task for you). Though many just prefer to rely on their own junk filtering, the more people reporting SPAM, the better the chances said SPAM will stop. This extension works with Thunderbird 17-19.
3. Email Security Plus
Email Security Plus is a powerful Anti-spam filter for Thunderbird. This addon will automatically check incoming emails and automatically delete any email marked as Junk. You can change the SPAM aggressiveness from low to high as well as create a blacklist for senders. Email Security Plus also allows you to show the X-Spam-Status and the Receiver headers in the extended header view. If you find that the built-in Thunderbird SPAM filter isn't working well enough, Email Security Plus might be just what you need. This extension works with Thunderbird versions 3-19.
4. Security Settings from Address Book
Security Settings from Address Book has an odd but telling name. The gist of this plugin is simple: It works with the Address book's Custom1 field (in the Other tab). If that field contains either (or both) "encrypt" or "sign" it will automatically encrypt or sign the outgoing email to that contact. The only caveat to this is that you must first set up the built-in encryption tool, which means working with a third-party to obtain a certificate (or you can use OpenSSL to create the PKCS12 certificate). This extension works with Thunderbird versions 7-20.
5. Master Password
Master Password is a handy extension that allows you to set a master password for Thunderbird. Without that master password, Thunderbird cannot be successfully started. It is also possible to set an auto lock which will require the password to be entered. You can even set Thunderbird to lock upon minimize as well as establish hot keys. This is a powerful addon and you want to make sure to not forget the password used or you could wind up having to manually remove the extension in order to get back into Thunderbird. This extension works with Thunderbird versions 3.1-22.0a1.
If you're looking for the means to secure Thunderbird, look no further than one (or more) of these easy to install (and free) addons. You can gain a good deal of security, on different levels, for your email. Just remember, if you're opting to go with an encryption option, make sure you understand the fundamentals of encryption before you dive in.