The Ultimate Guide To Accessing OST Files In Thunderbird

Updated on January 18, 2024 by Savita Sharma

Looking for safe and easy solution to Open OST file into Thunderbird mail client, you are at right page. On this page, you will learn how you can use your OST files in Thunderbird. Microsoft Outlook is a mail application that stores its file in OST format, and Thunderbird is a mail client that uses a MBOX format. So these both have different file formats no need to worry; you can easily use your OST file in Thunderbird. Before discussing the method, let us briefly discuss the OST file and MBOX file of Thunderbird.

Offline Storage Table (OST)

OST file is an offline copy of the user’s mailbox stored on the Exchange server. It enables users to access all the data stored in the mailbox when the Exchange Server is unavailable. OST files store complete mailbox including emails, contacts, drafts, notes, calendars, etc.

Thunderbird (MBOX File)

Thunderbird is an email client which stores its file in MBOX format. Multiple email clients save their files in MBOX format, and Thunderbird is one out of them. It is an open-source and free email client that easily saves entire mailbox data. Thunderbird can be used on multiple platforms like Windows, Mac, Linux, and Ubuntu operating systems.

Reasons Why Users Import OST to Thunderbird:

1. Cross platform support: Thunderbird is a type of cross-platform mail client that can be used on multiple platforms like Windows, Mac, Linux, and Ubuntu operating systems. Thunderbird is the default client of Ubuntu.

2. Secure: It has high security features as compared to other email clients

3. Small user/Organization: If a user/organization has less dealing through Email, then they may shift from a paid email client to a freeware Email client.

User can use the Export option inbuilt in MS Outlook for exporting the OST file. Still, it is not considered a convenient method for migrating because it does not assure conversion insecure manner. So you can use Third party tool for complete and accurate migration of OST files into Thunderbird email client. One best-recommended tool which is easily affordable with all the advanced and required features is Regain OST to MBOX Converter. This tool can migrate OST files without the installation of Outlook.

Manual Method to Open OST files in Thunderbird

There is no direct method available in the market to access OST files in Thunderbird. Here we explain the manual method in detail, it is divided into 2 steps. Follow the instruction given below:

Steps to Open OST Files into Thunderbird

Step 1: Convert OST into PST file

Step 2: Now Import this PST file into Thunderbird

Step 1: Convert OST to PST File

Following are the steps to convert OST to PST file.

  • 1. Open MS Outlook and choose File Tab
  • 2. Now Select Open and Export and click Import/Export button
  • Open OST Files into Thunderbird using manual method
  • 3. Select Export to a file option, Click next
  • Steps to Easily Access OST Files in Thunderbird
  • 4. Now Select Outlook Data File (.pst), click next
  • Step 3
  • 5. Select the Folders which you want to Export, click next
  • Effortless Ways to Import OST Files into Thunderbird
  • 6. Given the location where you want to save the PST file, click Finish
  • Step 5
  • 7. Now your PST file has been saved successfully

Step 2: Now Import the PST file into Thunderbird

In the previous step, we convert the OST file into PST format, now in this step we open this PST file into Thunderbird, Here are the steps:

  • 1. Launch Thunderbird email client and choose the Menu option
  • 2. Click Tools and then select the Import button
  • Steps to import OST into Thunderbird
  • 3. Here, you need to select Mail, or you can select the Import Everything option with click Next.
  • 4. Select Outlook and click next
  • Seamless Integration of OST Files in Thunderbird
  • 5. Now Select the PST file, which you want to import to Thunderbird
  • 6. Select the Folder where you want to import the messages and initiate the process
  • Step 3
  • 7. Now you have successfully imported the OST file into Thunderbird.

Limitations of the manual method

  • 1. Need technical skill to perform the conversion task
  • 2. Long process, minor mistake can raise the data loss issue

Alternative method to open OST files in Thunderbird

Conversion of OST mailbox is very easy by using Regain OST to PST converter. Using this tool you can convert OST file to MBOX/EML file format and the converted files can be easily accessed in Thunderbird. Steps to be followed for converting OST file are:

  • 1) Install and Run Regain OST to PST Converter on Windows Operating system
  • 2) Click on Add file/Add folder and select the OST files
  • Import OST emails into Thunderbird
  • 3) Take Preview of OST file before migration in other format
  • 4) Select location for saving the file after conversion
  • 5) Next from saving option select ‘save to MBOX/EML’ option
  • Open OST file into Thunderbird
  • 6) Click Convert, files will be exported shortly.

Additional Features:

  • Instantly convert OST files in few clicks
  • No loss of data and maintains the original format of the data
  • Efficient to repair corrupt OST file and recover deleted or lost OST emails
  • Compatible with Microsoft Outlook 2019, 2016, 2013, 2010, 2007, 2003, 2000, 2002, 98 and 97
  • Export OST files in multiple formats PST, EML, MSG, MBOX, HTML, ICS, VCARD, Office 365, Live Exchange Server
  • Supports all windows edition i.e. Windows 10, 8.1, 8, 7, XP, Vista
  • Detailed preview of emails before conversion
  • Allow to Import OST data files to Office 365 account
  • Easy handling of bulky files
  • Download free trial version and Save 30 emails per folder at Free of cost


On the above page, we have discussed how one can run his Outlook OST files into Thunderbird mail client. Data stored in OST format is important for every user, so no one will compromise with their data. If anyone can compromise with their data, then the export option of Outlook can be used, but the first and last recommendation of every expert is to use a third-party tool. One can use reliable software i.e., “Regain OST to PST converter” this tool is straightforward to use and provides results in very less time.

Frequently Asked Questions

Ques1. How does Regain Software help me to open OST files in Thunderbird?

Ans. Thunderbird supports MBOX file format, if a user wants to view an OST file in Thunderbird, First it is converted into MBOX format. And Regain OST Converter can do this in just a few clicks. After converting OST to MBOX file, you can import this file into Thunderbird email client.

Ques2. I have 20 OST files and want to access these OST files into Thunderbird email client, How can I do this?

Ans. Many reasons available on the internet to move data from Outlook to Thunderbird. You can perform this task by using the Manual method or using a professional tool. Manual methods have many limitations while the professional tool does not. You can add 20 OST files in the software, Scan and Convert them into MBOX format. And you can import these files into Thunderbird.

Ques3. Does this tool allow me to open several Huge OST files into Thunderbird in one go?

Ans. Yes, the software is fully capable to perform this task in an easy way. You can also split large files into small sizes before saving into MBOX format.

Ques4: Can we directly convert OST to MBOX with the manual way?

Ans: No, there is no manual method that can directly convert OST to an MBOX file format, but by using the advanced tool developed by Regain Software, you can directly and efficiently convert to MBOX.

Ques5: As I can see, there are multiple file formats as the target, like MBOX, PST, and EML; can I save the OST file into MBOX as well as PST file format in a single process?

Ans: If you want to open an OST file in Thunderbird, then you must convert OST to MBOX in a manner to add and open in Thunderbird. If you also want to open an OST file in any other Outlook email client, then convert to PST. However, in one process, you can opt for only one file format.

Ques6: Will I get all my emails of the OST file with the attachment in the Thunderbird in the same hierarchy if I convert OST to MBOX using the Regain OST Conversion utility?

Ans: Using Regain’s conversion utility, you can convert all the items, including emails, tasks, calendars, contacts, et cetera, in MBOX. And finally, by simply adding MBOX to Thunderbird, you can access it in Thunderbird.

Ques7: What are some common reasons to shift from Outlook to Thunderbird for which users want to open OST in Thunderbird?

Ans: Thunderbird is an open-source cross-platform that is available for Windows, Linux, macOS, and Unix. Also, this open-source, free platform is the best suitable for individual users. Also, users can add and run any email client on Thunderbird.