As you all know Thunderbird is a very famous email client that is used by millions of users in the world. But it has some drawbacks, that is why we need a better option to replace it. Office 365 is a better option which comes with multiple advanced features like-
1. Anywhere accessibility, not dependent on system for Office installation.
2. Office 365 application comes with more user friendly services like Teams, Yammer, SharePoint, etc.
If you want to migrate Thunderbird emails to Office 365, without installing any third party application on your system. You can try this free manual method which is a very convenient way to migrate emails. To get detailed information about the method, click on the link: https://www.datarepairtools.com/blog/migrate-thunderbird-mbox-to-office-365/