Thunderbird is one of the most popular free email clients. It supports plugins which can extend a standard functionality and provide a user new powerful tools and features. Thunderbird add-ons can be developed in the next cases:
Message Processing Workflow
Thunderbird add-ons help to automate emails handling workflow. It can be very helpful if you have some specific rules by handling incoming or outcoming emails.
Appearance and Customization
Add-ons can change a standard appearance of Thunderbird and make it more stylish and attractive as well as add some customizations.
Cloud Services Integration
It is possible to make Thunderbird much more convenient by integrating it with some cloud-based services. You can store your messages, contacts or anything else in the cloud.