By default, automatic updates are enabled in Thunderbird. We recommend you keep this feature so your users can have the latest security patches and features. You can ensure that automatic updates are installed without user interference by using the AppAutoUpdate policy.
If you need to turn off automatic updates, you can do this using the DisableAppUpdate policy.
For more information on policies, see Managing Thunderbird policies.
Beta builds of Thunderbird allow you to test features before they are released to the regular version of Thunderbird. They are a good way to identify issues with upcoming features and updates before they are released to the rest of your organization.
To download beta builds or daily test builds of Thunderbird, see The future of Thunderbird (Beta channel / Nightly channel).