You can help, even if you have no prior experience helping. You help another user, or help make Thunderbird better and enjoy the satisfaction that you have contributed to improving Thunderbird.
Below are just a few ways you can contribute to the Quality of Thunderbird. Each item has a specific page with more details.
This activity is simple, takes the least amount of time, and doesn't require any special skill.
More information here if you want to help with the testing activity.
Moderate: Maintaining the bug database
The bug database aka bugzilla is the tool used track defects. The bug database is open to anyone who wants to help developers know about issues with Thunderbird.
Work in this area requires some experience just using Thunderbird (just a few months), and the ability to determine what the user reporting a problem might be seeing. You don't need great technical skill. It just takes a little time.
More information on this activity can be found here.
- this is the #tb−qa channel on irc.mozilla.org