We have a new #OpenPGP passphrase protection feature in #Thunderbird Daily (development) builds, in response to requests we received in the past. Here's a description and call for testing:
https://thunderbird.topicbox.com/groups/e2ee/Tdc427a8b0255b85a/passphrase-protection-for-openpgp-secret-keys
I'd welcome some testing and feedback.