How to manually import Thunderbird to Microsoft Office 365?

It is well known that Mozilla Thunderbird stores data in MBOX and Maildir file format in the local machine, whereas Microsoft Office 365 is a cloud platform.

So migrating Thunderbird email directly to Office 365 is like migrating between two different platforms.

Still, the user keeps searching for converting Thunderbird to Office 365. So I would like to share the manual procedure to transfer the TB mailbox to the O365 account, which will help you do the conversion with the right guidance.

Method 1: Switching from Thunderbird to Office 365 Manually

The whole process is completed in 2 phases.

  1. First Export Thunderbird mailboxes to PST
  2. Migrate PST file to Office 365 using Microsoft Network Upload method

Method 1 (A): Convert Thunderbird to PST manually

  • Download, install and configure Eudora in the same system, where Microsoft Outlook is already installed.
  • Copy Thunderbird MBOX file and paste it in Eudora default location. 
  • Now change file extension: filename.mbox == filename.mbx
  • Run Outlook and click on the Import-Export tool
  • In Wizard, select “Import Internet mail & address” then click on the Next button.
  • Choose Eudora 2x, 3x, 4x (pro and light) option then next.
  • Browse the Eudora location and select your Thunderbird mailbox, then click Next.
  • Save the destination to save Thunderbird in Outlook and click on the finish button.

After importing Thunderbird emails to Outlook, you can export PST files from MS Outlook using Import-Export Tool or Visit the destination path to get your PST file.

Method 1 (B): Migrate PST to Office 365 using the Network upload method

If you are familiar with the Office 365 functionality, this process is much easier for you. 

  • Copy the SAS URL and download AzCopy
  • Upload your PST files to Microsoft 365
  • Create the PST Import mapping file
  • Create a PST Import job
  • Filter data and start the PST Import job

You can read step by step procedure here:

Alternative method: Thunderbird to Office 365 Migration Tool

Manually users have to go into a long process, affecting the folder hierarchy. In such a case, you can also adopt a small way to import your Thunderbird Email in Office 365.

I want to recommend MailsDaddy Thunderbird to Office 365 Migration Tool to move Thunderbird data to Office 365 mailbox. With this single solution, you will transfer direct Thunderbird data into Office 365 along with the folder structure, and it is also capable of migrating Thunderbird Maildir Mailbox.

Importing Steps for Thunderbird to Office 365

  • Download, install and run the application.
  • Add Thunderbird emails by clicking the Autoload button
  • Click on the Export button and select the O365 option
  • Select mailbox: Primary or In-place archive then next.
  • Fill in the log-in detail and press the sign-in button.


Here I have shared information about Thunderbird to Office 365 migration by which users can import data manually or use a solution. You can try the free demo version of the software and migrate 20 emails from each folder.

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