Collections are groups of related add-ons that anyone can create and share. Explore collections created by other users or create your own.
Thunderbird Add-ons? Here's Some Great Ones!
Thunderbird add-ons that I've either used for years, or tested and highly suggest.
Mozilla Labs Messaging Add-ons
The add-ons included in this collection are all ones that are part of the messaging category on Mozilla Labs: https://mozillalabs.com/messaging/
To create your own collections, you must have a Mozilla Add-ons account.