What is an MBOX File?

Supportin OS: Windows, Linux, Unix and Mac
File Category: Email File
Organization: Mozilla
MIME Type: Text/x-mailbox

MBOX stands for Mailbox. MBox file format represents a container for a collection of electronic mail messages. MBOX is a file extension for a text file that is used for storing and organizing a collection of email messages. The MBOX file is supported or created by several email applications like SeaMonkey, Thunderbird, Apple Mail, etc. The most used format for storing e-mail messages on a hard drive is the mbox format, in which all the messages are stored as a single, long, text file. The messages are stored inside the container with their attachments.

A message in the MBOX file format is specified by "From" with a white space character and at the end of every message, it is specified with a blank line. "From" means the line in the messages and the header starts with F,r,o,m, and space.

MailBox File Format

It is a type of email file, which stores messages in plain text format. The MBox file format remained non-standardized for a quite long time until 2005. Each message in Mbox begins with a separate line that identifies the message sender, and also the date and time at which the message was received. Well, there are some variants of MBOX file formats: mboxo, mboxrd, mboxcl, and mboxcl2. These will be clear to understand as mentioned:

Mboxo: It is different from the original Mailbox file because it uses constant strings like "???@???". Original MailBox uses the email address of the sender.

Mboxrd: It is basically the variation of mboxo mailbox, where the initial point of a message is described either in form of header or body.

Mboxcl: This format of the MBOX file is operated in 'Unix System v'. When new mail is appended to the mboxcl mailbox, it is transformed into the file before appending.

Mboxcl2: It is similar to mboxcl. It does not scan for 'From' lines. Each mboxcl2 comprises the content-length attribute in its header part.

Stored Location

MBOX stores all its data at a default location. There is no native location where one can find the MBOX file. Well, depending upon the email application and platform.

Location of MBOX file:- /user/library/mail/mailboxes/directory

Note:- Location of the MBOX file depends on the operating system

How to Open & View Mbox file?

If you are using Mozilla Thunderbird, SeaMonkey, Apple mail then you can directly import the .mbox file in these applications with attachments.

If you are not using any of these email clients then you can use third-party applications. MBOX file viewer is a user-friendly tool that doesn't require any supportive email client to access email messages. Users can open and view MBOX file messages easily on their local system.

Major Issues Faced With MBOX File

While users working with the MBOX file, users might encounter some errors, which could delay the whole procedure. Some of the most observed issues are given below:


MBOX file extension is supported by various email clients for the storage of the database. MBOX files are the most significant e-mail files that are the most reliable source of communication for business purposes. After understanding the various aspects of files, we have represented the entire information to let the users understand what is MBOX file structure and its specification details. We have also discussed the major issues while accessing the MBOX files.

Want to Move MBOX Files?

RecoveryTools MBOX Migrator is a safe and excellent tool that allows users to transfer emails from MBOX files to various email clients as well as to file formats like PST, EML, MBOX, PDF, etc. MBOX Exporter is 100% Virus Free and Safe software for importing MBOX files to various email clients online, as well as saving MBOX files in various file formats on Windows OS.

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