MBOX extension is a plain text file which holds the email messages as 7-bit ASCII text and the attachments are stored in encoded format. Generally MBOX file is used for storing or organizing messages in a single text file which also stands for MailBox. The starting of each message is specified by "From" tracked by a white space character and end of each message is specified with a blank line.

• mboxo: It is main Mbox format which uses the constant string "???@???" in place of sender's e-mail address.
• mboxrd: It is variation of mboxo mailbox format.
• mboxcl: It is the mailbox format used by Unix 'System V' mailboxes.
• mboxcl2: "mboxcl2" mailbox format is similar to mboxcl.

The MBOX file comes under the category of Database Files.

The MBOX file is supported by 20+ desktop mail clients some of them are elaborated below:

text/x-mailbox

Hex Signature: 00 0D BB A0

The default location of MBOX file is "/User/Library/Mail/Mailboxes/directory". The default location of MBOX file also depends on the email client. So this location may change for other mail clients.

• Apple Mail: /User/Library/Mail/[account]/INBOX.mbox/Messages/
• Mozilla Thunderbird: C:\Users\\AppData\Roaming\Thunderbird\Profiles\
• Entourage 2008: C/Users/user_name/Documents/Microsoft User Data/Office 2008 Identities/Main Identity
• Thebat: C:\Users\\App Data\Roaming\The Bat\Mail\profile folder
• PocoMail: C:\Documents and Settings\Administrator\Application Data\PocoMail\Mail.
• Mulberry: C:\Documents and Settings\Administrator\Application Data\Cyrusoft\Mulberry\Mailboxes
• Evolution Mail: C:\Documents and Settings\Administrator\.evolution\mail'
• SeaMonkey: C:\Documents and settings\Administrator\ApplicationData\Mozilla\SeaMonkey\Profiles\nz8lvw59.default\Mail.
• Netscape: C:\Documents and settings\Administrator\ApplicationData\Mozilla\Profiles\default\2yv6fh2e.slt\Mail.
• Opera Mail: C:\Documents and Settings\Administrator\Local Settings\Application Data\Opera\Opera\mail\store\account1

The MBOX or MBOXO or MBOXRD are types of Mail Box files that are used by various open source softwares. Hence, this file extension can be opened using all these applications that generate MBOX file. For Example, Thunderbird, SeaMonkey, Evolution, SeaMonkey and more.