Download and launch SysInfo Thunderbird to Office 365 Converter on your system.

Choose the Mozilla Thunderbird File Path from which you want to take data for conversion.

Then, click on the Next button to continue and view all files and folders.

Now you can see all the files, folders, and sub-folders of your Thunderbird account in a Tree-Structure form.

Mark the emails that you want to migrate from Thunderbird to Office 365 and click on the Preview button to see a particular email data and attachments. Click Next.

In the Save As option, choose Office 365 and log in through Modern Authentication.

You will receive an Authentication Successful Message once the Office 365 Login Process is completed.

You can Remove Duplicates on the basis of To, From, Subject, Cc, and Body once you checkbox this option.

Choose this Migrate or Backup Emails Without Attachment Files option to migrate emails from Thunderbird to Office 365 without attachments.

Apply the Date Range Filter to filter all the emails as per a specific date. Enter the start date and end date for specific mail migration.

You can give a Custom Folder Name to the resultant folder by this option. It will help in quick identification.

Finally, click on the Convert button and all your Thunderbird emails will be exported to Office 365.

After the completion of the conversion process, you will receive a confirmation. Click OK.

You can even download the report of the conversion process through the Download Report button.