How to Migrate Thunderbird Mbox to Office 365 Efficiently

Frosty Orange Tech Space


Thunderbird email client saves it mailbox data in MBOX file format. This MBOX file can store a large number of emails and attachments in a concatenated way. Developed originally for Unix system, due to its simplicity and effectiveness, over time more than 21 email applications support it now. These clients include Mozilla Thunderbird, Mac Mail, and even Gmail(via Google Takeout).

So in scenarios where any of these MBOX supported email clients' user switches to Office 365, there exists the requirement of MBOX to Office 365 migration solution.

Multiple Methods to Export Thunderbird to Office 365

Since there are a number of strategies for exporting the MBOX files to Office 365, organizations adopt those which are more feasible for them. There are some manual ways, some automated software solutions and even a mix of manual and software solution to achieve desired results. Here we will be discussing one of each of them and see if they are safe or inhibit any kind of risks. So let us start with the manual solution first.

Manual/Mixed Way to Migrate Thunderbird MBOX to Office 365

In this segment, we will share a method which requires two phases to be implemented for process completion. These two phases are:

I. Convert the MBOX of Thunderbird or other email clients into PST format

II. Implement Office 365 import feature and import the PST file.

Step I: Manual Way to Create PST Files:

  • Open the email client i.e., Thunderbird
  • If your MBOX file is an orphan one/ from other application, simply import it inside Thunderbird using ImportExportTools add-on
  • Create a new folder on your system desktop
  • Select all the emails that you wish to migrate and right-click, go to Save-as and save them all in the newly created folder
  • Now quit Thunderbird and open the Outlook application
  • Drag all the emails from the new folder and drop them inside any Outlook folder
  • Now locate and share the Outlook PST file over the network

Alternative Way for Creating the PST files:

In many cases, users are not aware of the easiest of ways that can make their Thunderbird to Office 365 migration a piece of cake. Instead of using the lengthy manual way laced with data loss risk factors, one can go for a reliable MBOX to PST Converter software. It will not only save the users time and effort but also nullify any chance of data loss or data manipulation throughout the conversion.

Nevertheless, once the PST files are created from Thunderbird MBOX, the next step includes importing them into Office 365 environment.

We will now give a brief explanation of the import process of Office 365 in order to move the Outlook PST converted from MBOX to Outlook PST

Step II: Office 365 Import Option

Now, we will be using the Import service of Office 365 with the help of a tool – Microsoft Azure AZCopy. Find the brief steps below:

  • Download and Install the Microsoft Azure AzCopy tool.
  • You will also require to copy your organization's SAS URL.
  • Then use the AzCopy.exe in Command Prompt to upload the files
  • Afterward, create a mapping file in CSV format
  • Finally, the PST file can be imported in Office 365.

For detailed steps, you can refer to the official Microsoft guide here.

Direct Method for Thunderbird MBOX to Office 365 Migration

Since each organization has its own preferences and requirements, some may implement the above defined mixed approach. Small firms may even go for the complete manual solution. But of course, there are organizations for whom the mixed or manual approach will not suit their needs. In such cases, a direct migration solution is preferred over the native ways.

SysTools MBOX to Office 365 Migration is the perfect approach to follow in this scenario. Its advanced algorithms help users to export Thunderbird to Office 365 in an efficient manner. All it takes is just 3 simple steps

  • Run the wizard and select MBOX files(using File or Folder mode)
  • Select the Office 365 radio button along with folder structure maintenance option
  • Choose from export the Thunderbird MBOX file contents with or without impersonation to Office 365

That's it, all the content from Thunderbird or any other email client MBOX file will be transferred to the preferred Office 365 account.

Going along with this simple procedure, one can also filter the emails, batch convert the MBOX files, and many more. All of this on an interactive GUI which guarantees a user-friendly experience.


A variety of reasons generates the requirement of migrating MBOX to Office 365. It can be exporting the data of Thunderbird to Office 365 or any other MBOX supported email client, but the general requirement remains the same. Personal users or organizations, both have specific conditions that must be fulfilled during this migration scenario. And the method they choose for completion of such task directly reflects their needs.

After considering all these factors, we came up with this article which consists of different routes for MBOX to Office 365 conversion. Some may prefer the complete manual approach while for some a mixed approach using MBOX to PST Converter will be beneficial. Since it will reduce any chances of data loss. While for others who are not willing to take any risks, a Thunderbird to O365 software will be the perfect way to go.