You can quickly import Thunderbird emails to Office 365 files with the right method available, eSoftTools Thunderbirds to Outlook Converter tool, that can convert individual or batch MBOX files to PST files without losing any information. Users can also bulk transfer Thunderbird files to PST or other formats like HTML, YAHOO, EML, EMLX, OFFICE 365, and MSG. It can also run on every Windows version up to and including Windows 10. It will also come with a free demo that allows the user to convert the first 25 Thunderbird emails to PST files for free.
For more info:- Import Thunderbird emails to Office 365
For more info:- Import Thunderbird emails to Office 365