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How Do I Import Emails from Outlook to Fastmail Account?

Ritu Roy | file conversion How to's Outlook Software Technology | 6 minutes read | Modified on: 15-01-2026
import pst to fastmail

If you’re looking for a way to import emails from Outlook to Fastmail along with email attachments, this guide will provide clear and practical solutions. In this blog, we will cover both manual and professional methods to help you transfer your PST data to Fastmail efficiently. By the end of this post, you will be able to complete the import process without losing any data, ensuring full integrity of your emails and attachments.

Fastmail is a widely used email service known for its security and reliability. It offers both free and premium account options. Many users who want to switch to a more streamlined and secure email platform choose Fastmail for its advanced email management features. Fastmail can be accessed from anywhere with an internet connection, making it convenient for personal and professional use.

On the other hand, PST files are Outlook data files that require an email client to access. This often creates a challenge when users want to migrate their emails to web-based platforms like Fastmail.

Can I Open a PST File in a Fastmail Account?

The short answer is no; you cannot directly open a PST file in a Fastmail account. Fastmail does not support the PST format natively.

To access PST emails in Fastmail, you first need to convert the PST file into a compatible format, such as MBOX. Once the conversion is complete, you can easily import the emails into your Fastmail account.

In the next section, we will walk you through the step-by-step process to import PST files into Fastmail, ensuring that all your emails and attachments are transferred safely and accurately.

How to Import PST to Fastmail Manually

You can manually import emails from Outlook to Fastmail, but it requires careful execution of the following steps:

Step 1: Import PST Files into Outlook

  1. Open Microsoft Outlook on your computer.
  2. Go to the File menu in the navigation bar.
  3. Select Open & Export from the available options.
  4. Click on Import/Export to start the import wizard.
  5. Choose Import from another program or file and click Next.
  6. Select Outlook Data File (.pst) as the file type to import.
  7. Browse your computer to locate the PST file you want to import.
  8. Click Finish to complete the import.
  9. Once imported, drag and drop the PST content into your main Outlook account to make the emails accessible.

Step 2: Using Thunderbird to Convert PST to MBOX

Before you can import PST files into Fastmail, you need to convert PST file into MBOX format, which Fastmail supports. Mozilla Thunderbird can help with this process. Follow these steps carefully:

  1. Download and install the Thunderbird application on your computer.
  2. Launch Thunderbird and add an email account of your choice to set up the application.
  3. From the navigation bar, click on Tools and select the Import option.
  4. In the import wizard, click Continue to proceed.
  5. Select the folders you want to import from your PST file by ticking the relevant checkboxes.
  6. Click Continue to move to the next step.
  7. On the final page, click Start Import.

Thunderbird will then automatically import all your Outlook data. It also organizes your emails into separate folders within Thunderbird, making it easier to manage and prepare for the next step, importing into Fastmail.

Step 3: Install the Add-on Extension in Thunderbird

To export your emails from Thunderbird in a compatible format, you need to install the ImportExportTools NG extension. Follow these steps:

  1. Click the gear icon in Thunderbird to open the Settings menu.
  2. Navigate to Add-ons and Themes.
  3. Search for ImportExportTools NG in the search bar.
  4. Once the extension appears, click Add to Thunderbird to install it.
  5. After the installation is complete, the extension is ready to use.

This add-on allows you to export emails from Thunderbird in MBOX format, which can then be imported into Fastmail.

Step 4: Create an MBOX File in Thunderbird

After importing your PST data into Thunderbird, the next step is to export it as an MBOX file so it can be imported into Fastmail. Follow these steps:

  1. Navigate to the folder you created in Step 2.
  2. Right-click on the folder you want to export.
  3. From the context menu, select ImportExportTools NG.
  4. Choose Export Folder from the available options.
  5. Click on As MBOX File to set the export format.
  6. Select the destination on your computer where you want to save the MBOX file.
  7. Click OK (or Save) to complete the export.

Your emails are now saved in MBOX format, ready to be imported into your Fastmail account.

Step 5: Import the MBOX File into Your Fastmail Account

Once you have your emails saved in MBOX format, you can import them into Fastmail by following these steps:

  1. Open Fastmail in any web browser.
  2. Log in using your Fastmail account credentials.
  3. In the dashboard, click the gear icon to open the settings menu.
  4. Navigate to the Migration section and select the HEY (upload MBOX file) option.
  5. Click Upload File and select the MBOX file you exported from Thunderbird in the previous step.
  6. Wait for the upload to complete. Depending on the size of your file, this may take a few minutes.

Once the process is finished, your emails will be available in your Fastmail account. By carefully following these steps, you can successfully import emails from Outlook to Fastmail using the manual method.

Limitations of the Manual Method

While this manual approach works, it has several drawbacks:

  • Risk of data loss: Any mistake during the process can lead to missing emails or attachments.
  • Time-consuming: The process involves multiple steps and can take a long time, especially for large PST files.
  • Technical knowledge required: Users need a basic understanding of Outlook, Thunderbird, and Fastmail settings.
  • Attachments may be lost: Some emails may not retain their attachments after conversion.
  • Not suitable for bulk data: Large mailboxes or multiple PST files can make the manual process impractical.
  • Step complexity: Skipping or performing any step incorrectly can prevent successful migration.

Because of these limitations, many users prefer a professional automated solution for importing PST files to Fastmail efficiently and safely.

How to Import PST to Fastmail Professionally

If the manual method does not deliver the desired results, you can use the CubexSoft PST Converter tool for a faster and more reliable solution. This professional software allows you to directly import emails from Outlook to Fastmail account while maintaining complete data integrity, including all emails and attachments.

The tool features an easy-to-use interface, making it suitable for both beginners and advanced users. You can download the free trial version to test the functionality and see how efficiently it works before purchasing the full version.

To learn the complete process and get a direct solution for importing PST files into Fastmail, follow the step-by-step method described below.

Steps to Import PST Files into Fastmail Using a Professional Tool

Using a professional PST file conversion tool simplifies the process and ensures that all emails and attachments are transferred safely. Follow these steps:

  1. Launch the PST to IMAP Converter application on your Windows or Mac computer.
  2. Click Add Files to load the Outlook PST files or folders you want to import.
  3. Review the loaded files, select the ones you want to migrate, and click Export.
  4. From the list of available saving options, choose IMAP.
  5. Enter your Fastmail account credentials: email address, password, and IMAP host details.
  6. Click Convert to start the migration process.

The tool will automatically upload your PST emails to your Fastmail account, keeping all attachments and folder structures intact. This method is faster, more reliable, and ideal for large or multiple PST files compared to the manual approach.

Benefits of Using the Professional Method

Using a professional PST to Fastmail tool offers several advantages over the manual approach:

  • Selective Import: You can choose which PST files or folders to import, avoiding unnecessary data transfer.
  • Preserves Data Integrity: All emails, attachments, and folder structures are maintained during the migration process.
  • Direct Migration: Import PST files straight into your Fastmail account without navigating through complex manual steps.
  • Attachment Support: The tool ensures that all attachments are transferred safely along with emails.
  • Wide Compatibility: Works with all versions of Windows (11, 10, 8.1, 8, 7, XP) as well as macOS.
  • User-Friendly: No advanced technical knowledge is required; the intuitive interface makes the process simple for anyone.

Final Thoughts

In this guide, we explained how to import emails from Outlook to Fastmail using two approaches: manual and professional. While the manual method works, it is time-consuming, complex, and requires technical expertise. On the other hand, the recommended professional tool makes the process fast, easy, and secure, allowing you to import multiple PST files with attachments while maintaining complete data integrity in just a few clicks.

For those seeking a quick and reliable solution, we suggest trying the free trial version of the tool. Once you confirm it meets your needs, you can upgrade to the licensed version for unlimited use.