Enigmail v0.8x for Thunderbird has received a new user interface! If you are familiar with Enigmail versions prior to 0.81.0, please read this information before proceeding.
Enigmail configuration is now split into two parts:
The account specific settings are available through the menu Tools -> Account Settings. For each account there is now an OpenPGP Security list item which holds the options specific for each account.
The PGP key settings from Enigmail v0.80.0 and earlier version are not converted into the new per-account settings. Enigmail is by default disabled for all accounts!
The common global settings have been cleaned up and merged into one dialog. The preferences are either available through the Enigmail menu, or by clicking the Advanced button in the Account Manager's OpenPGP Security Preferences.
A new option has been added that enables you to turn on encryption automatically if replying to an encrypted message. Note that this doesn't influence the settings for message signing.
The behavior of Enigmail has been adapted to be more similar to the behavior of S/MIME. A new OpenPGP button has been added from where the encryption / signature settings can be selected. The Enigmail menu does no longer serve for sending encrypted or signed mails, sending isdone uniquely from the normal Send button or the File -> Send menu. It is suggested that you try the new settings by sending a couple of mails to yourself before you use it actively, so that you understand the new behavior.
The settings for encrypting or signing a message are now visible in the lower right corner of the compose window, with small icons being displayed if signing or encryption is turned on.