If you installed the beta over the top of the release version (choice 2 above), then your process will be more complicated. Please consult this <a href="https://support.mozilla.org/kb/thunderbird-beta">beta support article.</a>
如果您使用测试版覆盖安装正式版（上面的第二种方式），那么操作会复杂一些。请见<a href="https://support.mozilla.org/kb/thunderbird-beta">测试版支持文章</a>。