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How To Migrate from Thunderbird to Office 365?

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Summary: As Office 365 offers various impressive features, people often tend to migrate from desktop-based email clients, such as Thunderbird, to Office 365. In this post, we’ve discussed different manual ways to move Thunderbird to Office 365.

In addition, we’ve mentioned a specialized MBOX converter software that can directly export Thunderbird mailbox data to Office 365.

Office 365, now Microsoft 365, is a range of subscription services provided by Microsoft. It contains cloud versions of core Microsoft Office applications such as Outlook, Excel, and Word. These services make collaboration and remote working easy and are backed by secure Microsoft servers.

That’s why many organizations prefer them over desktop-based email clients such as Thunderbird.

Why Migrate Thunderbird to Office 365?

Office 365 offers various benefits such as cost savings, flexibility, mobility, and increased collaboration. Following are some benefits for migrating from Thunderbird to Office 365:

  • Easy upscaling in Office 365 due to flexible plans and a range of features.
  • High accessibility with support for multiple devices.
  • Integration of commonly used applications such as MS Outlook, MS Word, MS PowerPoint, etc.
  • Advanced security features.
  • Integrated data storage, collaboration, and sharing features.
  • Reliable Microsoft servers that ensure maximum uptime and uninterrupted business operations.

How to Migrate from Thunderbird to Office 365?


If you are a Thunderbird user and want to migrate to Office 365, you need to transfer all your emails and other data from Thunderbird to your Office 365 account. However, there is no in-build function in Thunderbird to directly migrate the data to Office 365.

To ease with the process, below we have discussed some manual methods to move Thunderbird to Office 365 with stepwise instructions. Also, we’ve mentioned an MBOX converter tool that can help you directly transfer Thunderbird mailbox data to Office 365.    

Method #1: Transfer Emails as EML Files

You can migrate Thunderbird to Office 365 by downloading Thunderbird emails on your Desktop as individual EML files, and then exporting these files to Outlook.

Note: This process may take a lot of time if you’ve the large number of emails. You can use a specialized MBOX converter tool to directly transfer Thunderbird emails to Office 365 in a few clicks.

Follow these steps:

  • Create a folder My Emails on Desktop.
  • Launch Thunderbird and select the emails you want to migrate.
  • Right-click the emails and select Save As option from the menu.
  • Browse to My Emails folder and save the emails in the folder.
  • Now, launch Outlook and create a new subfolder in your mailbox where you wish to save Thunderbird emails.  
  • Select all Thunderbird emails in My Emails folder on Desktop. Drag these emails to the new Outlook mailbox subfolder and drop them there. The emails will be saved in the subfolder. 

Method #2: Forward Emails as Attachments

You can also forward your emails from Thunderbird to Office 365 directly as attachments (EML files).

Note: The emails won’t be directly visible in the Office 365 mailbox. You will have to open the EML files individually to view the emails.

To do so, follow these steps:

  • Launch Mozilla Thunderbird on your system.
  • Select the emails you want to transfer from Thunderbird to Office 365.
  • Right-click the emails and select Forward as Attachments option from the menu.
migrate to office365
  • Enter your Outlook email ID and click Send.
  • Verify the emails by opening Outlook inbox.

Automated Solution to Migrate Thunderbird to Office 365

The above-mentioned manual methods are viable when you have to migrate a small number of emails. If you have thousands of emails in your Thunderbird account, then it’s a time-consuming and tedious process to manually drag and drop them in Office 365, or forward them as attachments.

As an alternative, you can use an MBOX converter tool to transfer your Thunderbird MBOX database to Office 365 directly.

You can find Thunderbird MBOX files on your system by following these steps:

  • Go to Start Menu and search %APPDATA%.
  • In the Roaming folder where you will be taken to, find and open Thunderbird folder.
  • Open Profiles folder and open your profile folder. You will find the MBOX files in this folder.

An advanced MBOX converter tool such as Stellar Converter for MBOX- Technician can migrate Thunderbird to Office 365 automatically. The MBOX converter software is easy-to-use, with an intuitive interface.

You just need to launch the software, select the Thunderbird MBOX file, let the software scan the file, and enter the login credentials of your Office 365 account. The software then transfers all the mailbox data from the MBOX file to Office 365.


It’s not an easy task to migrate Thunderbird to Office 365 as you need to manually transfer Thunderbird emails to Office 365. For small mailboxes that have a few hundred emails, it is viable to manually drag and drop the emails or forward the emails as attachments.

However, if you’ve dozens of Thunderbird mailboxes with thousands of emails, then the manual approach can be tiresome and laborious. Therefore, a good option is to use a dedicated MBOX converter software that can directly export even large Thunderbird mailbox files to Office 365.