Paranoia
Paranoia add-on for Thunderbird. See who is reading your emails.
Install / Use
/learn @gjedeer/ParanoiaREADME
Check if your emails arrived TLS-encrypted (and which corporations were able to read it nevertheless)
Paranoia on Mozilla Extensions:
https://addons.mozilla.org/en-US/thunderbird/addon/paranoia/
Instructions (PL):
http://gdr.geekhood.net/gdrwpl/paranoia.php
