Encrypt Thunderbird Email with Enigmail

Sometimes email contains sensitive data which must be encrypted. You can handle this two ways, manually encrypt the data or use an exceptional Thunderbird Extension called Enigmail. This extension uses gpg and makes the encryption/decryption as user-friendly as it gets. With keys installed in Enigmail (either manually or from a keyserver) encrypted email is automatically decrypted and signatures are checked for validity. This makes using encryption for email a task even the new user can master.
If you do not have a key pair generated, Enigmail can even do this for you. So with this extension you can encrypt/decrypt email without having to touch the command line. Pretty sweet. Let's take a walk through this system.
I am going to assume you know how to install an extension in Thunderbird (I am also going to assume gpg is installed). Knowing that, install the Enigmail extension. Once this extension is installed (and you have restarted Thunderbird), you will notice a new menu entry called OpenPGP. This is where you take care of the setup of Enigmail.
Generate your key pair

The first step is to generate your key pair. This can be done either from command line or from Enigmail itself. From within Thunderbird click the OpenPGP menu and click the Key Management entry to open the key manager window (shown in the image to the left.)
Click on the Generate menu and select New Key Pair to open the key generation window (shown below to the right.)

From within this new window you have a number of options to consider (which are all fairly self explanatory.)For most instances the defaults will work. The only change you might make is if you do not want the key to expire click the Key Does Not Expire checkbox.
As the window says, during the generation process you will want to go about the business of using your PC in order to help randomize the process of key generation. This even holds true when you are generating keys via the command line in Linux.
If you already have a key on your machine (generated from the command line or some other tool) you can import that key from the same key manager tool shown above. Just click on the File menu and select Import Key from File.
Once your key has been imported into (or generated by) Enigmail you are ready to use Enigmail to encrypt your messages.
Encrypt and Sign a Message
Start composing a new email and you will notice the OpenPGP menu entry has been added. Once you have completed composing your email click on the OpenPGP menu and select Encrypt Message and/or Sign Message to encrypt and/or sign your outgoing messages with your key.

This brings up an issue. If you do not configure Enigmail to not encrypt/sign by default all of your outgoing messages are going to be encrypted and signed. This is a problem when the recipient doesn't have your key. I highly recommend configuring Enigmail to not encrypt/sign by default. To set this click on the OpenPGP menu entry in the MESSAGE COMPOSITION WINDOW (not the main Thunderbird window). From there click on the Default Composition Options sub menu and then select Signing/Encryption Options. A new window will appear (shown to the left.) Make sure you de-select all of the options in the Message Composition section. Now you have to manually choose to sign and encrypt each message. It's one extra step but your non-geek friends and family will thank you for it.
Decrypting
Like send mail, you have two options for receiving mail. You can have encrypted mail automatically encrypted or you can do it manually. Of course for either options you have to have the senders' key imported into the system.
If you click on the OpenPGP menu (in the main Thunderbird menu) you will see an entry for Automatically Decrypt/Verify Messages. If this is checked all incoming encrypted/signed mail will be decrypted/verified. If it is not checked you will have to do this manually by selecting the encrypted/signed email and then clicking the Decrypt/Verifyentry in the OpenPGP menu.
Final Thoughts
And that's it! Simple email encryption in Linux with Thunderbird and Enigmail. You can, of course, do this manually from the command line, but why make things difficult? If you have needs to encrypt/sign outgoing or incoming email, Enigmail is the perfect solution for every Linux and Thunderbird user. And for those BSD, Solaris, OS/2, Mac, or Windows users there is an Enigmail for you as well.
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You said that Outlook isn’t your main email client, so which is your main one?
I think its thunderbird
It is Mozilla Thunderbird.
Awesome! This actually solved my problem… what a stupid bug.
If this is the same bug that I’ve encountered, there may be another fix: (1) hover over open Outlook item in Taskbar, cursor up to hover over Outlook window item, and right-click; (2) this should give you Restore / Move / Size / Minimize / Maximize — choose Move or Size; (3) use your cursor keys, going arbitrarily N/S/E/W, to try to move or size the Outlook window back into view. Basically, the app behaves as though it were open in a 0x0 window, or at a location that’s offscreen, and this will frequently work to resize and/or move the window. Don’t forget to close while resized/moved, so that Outlook remembers the size/position for next time.
THANK YOU Claude!!! I could get the main window to launch but could not get any other message window to show on the desktop. You are my hero!!!!
Solved my issue! 6 years later and this is still problem…
Fantastic. Thank you. Size did the trick.
This solved my Outlook problem, too. Thank you. :)
Thank you so much, this started happening to me today and was causing big problems. You are a life saver, I hope I can help you in some way some day.
You are a god – thank you!
thanks a lot…. work like charm.. :-)
Yah…thanks Claude. I’ve been having the same problem and tried all the suggestions…your solution was the answer. It had resized itself to a 0/0 box. Cheers
Excellent post. This had me baffled even trying to accurately describe the problem. This fixed it for me.
Thank you
Thanks a lot for the article. Don’t know why it happenend, don’t know how it got fixed, but it was really annoying and now it works :-)
Thanks a lot. I was facing this issue from past 3 week. I tried everything but no resolution. The issue was happening intermittently and mainly when I was changing the display of screen ( as i use 2 monitors). The only option i had was to do system restore. But thanks to you.
I’ve been tried to sole this problem for 12hours. Your comment about changing the display of screen helped me a lot!! Thanks!!
Thank you…don’t know why this happened but your instructions helped me fix it. Running Windows 10 and office pro 2007
Great tip! Thanks!
Worked for me, too – thank you!!!
It’s Worked for me, too
thank you very much!
I had a similar issue with Outlook 2013 on Windows 10 and this helped me to fix it. Thank you very much!
Thank you so much. Solved!
Considering you published this in 2012, incredible not been debugged by Microsoft.
Thank you again. M
This problem was faced by only one user logging to TS 2008 r2 using outlook 2010.The issue was resolved.
Thanks.
Great tip. Thank you!!!! If it helps, I had to use the Control Key and the arrow keys at the same time to bring my window back into view. Worked like a charm.
Thank you, this worked !!!!
Man, you are a fucking god. Thanks a lot, what an annoying bug!!
Awesome, this post solved the issue. Many thanks!