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How to Import PST to Fastmail Easily Without Data Loss

Ritu Roy | how to imap mac os outlook PST software technology | 5 minutes read | Modified on: 06-02-2026

If you are looking for a reliable way to import PST files into Fastmail while keeping your email attachments intact, this guide is for you. In this blog, we explain both a manual approach and an alternative solution to help you move PST data into your Fastmail account. By the end of this article, you will understand how to complete the migration process smoothly while maintaining data accuracy and integrity.

Fastmail is a widely used email service known for its strong security features and clean interface. It offers both free and paid plans, making it suitable for different user needs. Many users choose Fastmail when switching email platforms for better organization and privacy. Since Fastmail is web-based, it can be accessed from anywhere with an internet connection. PST files, however, are Outlook-specific and cannot be opened without an email client.

Is It Possible to Open PST Files Directly in Fastmail?

The simple answer is no. Fastmail does not support PST files directly. To use PST data in a Fastmail account, the file must first be converted into MBOX format, which Fastmail supports for importing mailbox data.

Once the PST file is converted to MBOX, it can be uploaded to your Fastmail account. Below, we explain the manual method in detail.

Manual Method to Import PST into Fastmail

This method involves multiple tools and steps. Make sure to follow each instruction carefully to avoid errors.

#1: Import PST Files into Outlook

  1. Open Microsoft Outlook on your computer.
  2. Click on the File menu.
  3. Select Open & Export, then click Import/Export.
  4. Choose Import from another program or file and click Next.
  5. Select Outlook Data File (.pst).
  6. Browse and select the PST file stored on your system.
  7. Click Finish to complete the import.
  8. Drag the imported PST data into your primary Outlook mailbox.
  9. Once completed, proceed to the next step.

#2: Convert PST Data Using Thunderbird

Since Fastmail supports MBOX files, the PST data must be converted.

  1. Download and install Mozilla Thunderbird.
  2. Launch the application on your system.
  3. Add any email account to Thunderbird.
  4. Open the menu bar and click Tools.
  5. Select Import, then click Continue.
  6. Choose the folders you want to import.
  7. Click Continue and then Start Import.
  8. Thunderbird will import your Outlook data and organize it into folders.

#3: Install ImportExportTools NG Add-on

  1. Open Thunderbird settings by clicking the gear icon.
  2. Navigate to Add-ons and Themes.
  3. Search for ImportExportTools NG.
  4. Install the extension and restart Thunderbird if required.

#4: Export MBOX Files from Thunderbird

  1. Right-click on the folder created during the import.
  2. Select ImportExportTools NG.
  3. Choose Export Folder.
  4. Click As MBOX File.
  5. Select a destination folder to save the file.
  6. Your MBOX file is now ready.

#5: Upload MBOX File to Fastmail

  1. Open Fastmail in a web browser and sign in.
  2. Click the Settings (gear) icon.
  3. Go to the Migration section.
  4. Select Upload MBOX File.
  5. Choose the exported MBOX file and upload it.
  6. After a short wait, your emails will appear in your Fastmail account.

Drawbacks of the Manual Method

While the manual approach can work, it has several limitations:

  • High chances of data corruption or loss
  • Time-consuming and lengthy process
  • Requires multiple tools and technical knowledge
  • Risk of missing email attachments
  • Not suitable for large PST files or bulk data
  • One mistake at any stage can cause migration failure
  • Folder structure may not remain intact

Due to these limitations, many users look for a more reliable and efficient alternative when manual methods fail or become too complex.

How to Import PST to Fastmail in Bulk Using a Professional Solution

If the manual approach feels complicated or does not produce the desired results, using a professional migration tool is a smarter and more dependable option. One such solution is MacArmy PST Converter, which is specifically designed to simplify the process of importing PST files into Fastmail, especially when dealing with large volumes of data.

This expert tool offers a clean and intuitive interface, making it suitable for both technical and non-technical users. It allows direct migration from PST files to a Fastmail account while ensuring that no data is lost during the process. All mailbox items, including emails, attachments, folder hierarchy, and message properties, are transferred accurately.

A key advantage of this software is that it works independently of Microsoft Outlook. You can migrate PST files to Fastmail without installing or configuring Outlook on your system. Whether you need to move a single PST file or perform a bulk migration of multiple mailboxes, the tool handles the task efficiently while preserving complete data integrity.

Key Features of the PST to Fastmail Converter

The PST to Fastmail Converter is built to handle bulk email migration, allowing users to move multiple Outlook PST files into a Fastmail account in one go. Throughout the transfer, the tool keeps the original email layout, folder organization, and formatting unchanged.

The software is designed to be easy to use, even for users with no technical background. The process involves only a few simple actions, uploading the PST file, entering Fastmail account details, and initiating the migration.

To help users evaluate the tool before purchase, a free trial version is available. The demo edition allows the migration of up to 25 emails per folder, making it ideal for testing features and performance.

Step-by-Step Guide to Import Outlook PST Emails into Fastmail

Follow the steps below to move PST emails into your Fastmail account smoothly:

  1. Download and launch the PST to Fastmail Migration Tool on your system.
  2. Use Add Files or Add Folder to upload the PST files you want to migrate.
  3. Preview the loaded mailbox data and click Next to proceed.
  4. Choose IMAP as the destination export option.
  5. Enter your Fastmail email address, password, and IMAP server details accurately.
  6. Click Export to start transferring PST data to your Fastmail account.

Once the process completes, all selected Outlook data will be available in Fastmail.

Why Use an Expert-Recommended Tool for PST to Fastmail Migration?

IT professionals recommend using a dedicated Outlook to Fastmail converter because it offers several advantages over manual methods:

  • Directly transfers PST data to Fastmail without complex procedures
  • Uses IMAP for complete mailbox migration, including emails and attachments
  • Preserves folder hierarchy, email formatting, and message properties
  • Protects Fastmail login credentials during the migration process
  • Supports bulk import of multiple PST files at the same time
  • Works independently of Microsoft Outlook
  • Compatible with both Windows and macOS platforms

Final Thoughts

In this section, we discussed two ways to import Outlook PST emails into Fastmail. While the manual approach is lengthy and requires advanced technical knowledge, the professional solution offers a faster, safer, and more convenient alternative.

The recommended migration tool simplifies the entire process, allowing users to transfer emails, attachments, and mailbox folders with full accuracy in just a few clicks. It saves time, reduces effort, and eliminates the risk of data loss.

For users who want a quick and reliable solution, the free trial version is a great way to test the tool’s capabilities. Once satisfied, upgrading to the full version enables unlimited and seamless PST to Fastmail migration.