MBOX File Format – What is .MBOX Extension & How to Open MBOX?

MBOX file Extension is used by different email clients to store email messages into the plain text file. All messages in MBOX file format are stored one after another. The header part of each message starts with the “From” line and ends with a blank line. Initially MBOX file is implemented into the UNIX based system and now this file extension is supported by several other email clients like Mozilla Thunderbird, Apple Mail, Eudora Mail, Opera Mail and Postbox etc. Gmail also offers an option to backup mailboxes into the MBOX file format.

So in this article we will deeply learn about MBOX file Extension. We will try to explain each and every possible details about MBOX file format. Along with that we will also look into the structure of MBOX file format. After discussing all these things we will see the methods to Open MBOX file format. Please share this article with your friends if you are enjoying the same.

What is the Structure of MBOX File Format?

In MBOX file each message is saved in the plain text file. MBOX file format consists of four different types of MBOX Structures that are explained below:

MBOXO: In MBOXO format, the senders email ID in replaced with a constant string “???@???”. This file format stores the attachments into the separate folders. This variation of MBOX file format is used by Eudora email client.

MBOXRD: In this variation of the MBOX file format, the starting of the email message is specified in the form of Body or Header. All the email clients of Mozilla family use this variation of MBOX file extension.

MBOXC1: This variation of MBOX file format is used in UNIX by the System V mailboxes.

MBOXC2: This file format is also used by UNIX System V mailboxes and it is very similar to the MBOXC1 file format.

What is the Location of MBOX file Extension?

As mentioned earlier, MBOX file format is supported by several email clients and hence each email clients stores the MBOX file at different location. To locate the MBOX file in Windows 7 and above operating system, please use the steps mentioned below:

Locate MBOX File in Thunderbird Email Clients

Step 1: Open RUN (Window + R), type %appdata% and press enter.

Step 2: Now find the folder with the name Thunderbird, There you will find another folder with the name profile.

Step 3: There you can find all your MBOX files

Locate MBOX File in Eudora Email Client

Step 1: Open Run (Window + R) and type %appdata%\Qualcomm\Eudora and press Enter.

Step 2: From there select the Folder with the name Eudora where you can find all your MBOX file.

Locate MBOX File in Opera Mail

Use the path given below to locate the MBOX file in Opera Mail.

C:\Users\admin\AppData\Local\Opera Mail\Opera Mail\mail

Can we Open MBOX File in Windows Outlook?

You can easily open the MBOX file in all the MBOX supported email clients mentioned above. But if you need to open the MBOX file in Windows Outlook then you will need to convert the MBOX file into PST file format. To perform this conversion task, you can use CareUtils MBOX to PST Converter. Migrating MBOX to PST with this tool is quick and super easy. Even a non-technical user can easily perform the migration. After performing the conversion you can easily open the PST file in Outlook email client.


In this article we have discussed what MBOX File Extension is, Where the MBOX file is Located and How to Open the MBOX File. Hope you liked the article. Please share it with your friends if you loved our work. If you have any doubt or need any other information please comment below, we will respond as early as possible.

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