How to Migrate Thunderbird to Office 365 (Outlook 365) Easily
Jackson Strong | October 3rd, 2025 | Mozilla Thunderbird
Many users are moving from desktop-based email clients like Mozilla Thunderbird to cloud platforms such as Microsoft Office 365 (Outlook 365) for better accessibility, data security, and collaboration. However, Thunderbird stores data in MBOX format, while Office 365 works with PST or direct cloud synchronization, which makes the migration a bit tricky.
In this guide, you’ll learn two practical methods to migrate Thunderbird to Office 365 — a manual setup method and an automated solution — along with their pros and cons.
Let’s begin with the manual way.
How to Migrate from Thunderbird to Outlook 365 Manually?
If you prefer a free method, you can configure your Office 365 account in Thunderbird using IMAP and move emails manually.
Follow the step-by-step process below:
- Open Thunderbird and navigate to Add-ons.
- Install the Import/Export plugin.
- After installing the plugin, go to Dashboard.
- Now, click the folder that you want to import to Office 365.
- Navigate to Import/Export >> Export Folder.
- Now, name the folder to save at your desired location.
- Thunderbird will export the folder in .mbox file format.
- Restart and open the Thunderbird application again.
- Go to Tools and then Account Settings
- Click Account Actions and then Add Mail Account.
- Enter your Name and Office 365 email credentials.
- Click Remember password.
- Enter IMAP and SMTP details and click Done.
Once synchronized, these emails will automatically upload to your Office 365 mailbox in the cloud.
Limitations of the Manual Method
While the manual setup works, it has some practical limitations:
- You can migrate only one mailbox at a time.
- It requires manual reconfiguration for each account.
- Risk of data loss or missing attachments during transfer.
- Large mailboxes may take hours or even fail to sync.
If you have a large number of emails or multiple Thunderbird profiles, these issues can make the manual process time-consuming and unreliable.
How to Migrate Thunderbird to Office 365 Automatically?
If you want a faster and more reliable migration without complex setup, you can use a dedicated Thunderbird migration tool. One such tool in our suggestion is Advik Thunderbird Converter.
It directly connects Thunderbird with your Office 365 account, allowing you to:
- Transfer complete mailboxes with attachments and folder hierarchy.
- Select specific folders or date ranges for migration.
- Avoid syncing errors or duplicate items.
You only need to sign in with your Office 365 credentials, and the migration completes automatically — even for large mailboxes.
Now, click on the Free download link and check the working process.
Steps to Transfer Thunderbird Mail to Office 365
1. Launch the software on your Windows PC.
2. Once the software detects your profile, click Next.
3. Select email folders and click Next button.
4. Choose Office 365 from the saving option menu.
5. Enter your Office 365 login credentials and click Next.
Done! The software will start transferring emails from Thunderbird to Office 365 email account.
No other method or solution can beat this one. If you are one of the users looking for a solution to migrate from Thunderbird to Outlook 365, then you must try the above method.
Recommended for users who want a quick and error-free migration.
Check the video tutorial below for a better understanding of the complete working process.
Watch How to Migrate Emails from Thunderbird to Office 365
Conclusion
Migrating from Thunderbird to Office 365 is a common need for users moving to a cloud-based work environment.
If you only have a small mailbox, the manual IMAP setup is a suitable free option. However, if you manage large or multiple accounts, or want a time-saving, error-free process, using an automated Thunderbird to Office 365 migration tool is more practical.
Choose the method that fits your requirements and technical comfort level.
Frequently Asked Questions
Q1. Why should I migrate Thunderbird to Office 365?
Ans. Office 365 offers better accessibility, storage, data security, and integration with Microsoft Teams, Word, and Excel — making it ideal for professional use.
Q2. How long does it take to migrate emails from Thunderbird to Office 365?
Ans. It depends on the mailbox size and the internet speed. Manual methods may take hours for large data, while automated tools complete it faster.
Q3. Will my attachments and folder structure remain the same?
Ans. Yes, both methods can retain folder hierarchy and attachments if followed correctly.
Q4. Can I migrate multiple Thunderbird accounts to one Office 365 mailbox?
Ans. Yes, but it’s more efficient to use an automated migration solution for multiple accounts.
