Rated 5 out of 5 stars

yazan: End User tarih: Ara. 7, 2018 ·

Argh!!! Thunderbird 60 disabled this urgent addon!

Rated 5 out of 5 stars

yazan: End User tarih: Mayıs 31, 2017 ·

2017/05 here, addon still working.

Yet, making it working is not a trivial task.
Instructions:

1) Create and fill file like this:

A gentleman is someone who can play the accordion, but doesn't.
/Tom Waits/
%
Good... Bad... I'm a guy with a gun!
/Evil Dead 3/
%
Today's forecast is extra bomby, slight chance of mushroom clouds.
/Starcraft, Terran Ghost/

Note percent sign between phrases/quotes.
(Thanks dasoe's comment!)
For example C:\Fortune\cookies.txt

2) In addon options:
Specify "fortune cookie file"=C:\Fortune\cookies.txt
Specify "signature target"=C:\Fortune\currentcookie.txt
That is the file where this addon will put a random cookie every "Update signature every # seconds".

3) Menu\Tools\Account Settings:
Turn on "Attach the signature from a file" = C:\Fortune\currentcookie.txt

(Thanks Didereaux's comment!)

However, it's sad that this addon inserts empty lines before the cookie.