.mbox
MBOX file: what it is and how to open it
An MBOX file keeps many emails in one mailbox, such as a Google Takeout export. Our Android and Windows apps list the first 1,000 messages offline. Use Thunderbird or Apple Mail to import and manage a complete mailbox.
Drop your MBOX file here
Opens on this device. Nothing is uploaded. Any other file works too.
What is an MBOX file?
MBOX stores messages one after another in a single file. It is a family of mailbox conventions used by Unix mail tools and email applications. Google Takeout can export Gmail this way; Thunderbird’s local message folders can be mailbox files with no extension.
An MBOX is an archive of messages, not a connection to your inbox. Reading it does not sign in, send mail or synchronize changes. Keep an untouched backup before importing it into another email application.
What is inside
A separator line beginning with From and a space marks each message. The message then has headers, a blank line and its body. Attachments remain inside the message using email encodings, rather than separate files beside the mailbox.
MBOX variants differ in how they escape body lines beginning with From and how they mark message lengths. Our apps read mboxo and mboxrd quoting; they do not use Content-Length framing from mboxcl. An EML file is one message rather than a whole mailbox.
archive.mboxFrom sender dateseparator for message 1message headersFrom, To, Subject, Dateblank linethen body and encoded attachmentsFrom sender dateseparator for message 2message headers and bodythe next complete emailHow to open an MBOX file
Windows
- Thunderbird with ImportExportTools NGFree. The add-on imports MBOX into local mail folders so you can manage the messages in Thunderbird.
- Universal File Opener for WindowsOursLists the first 1,000 messages by subject, sender and date offline. Open a message to read it and access attachments.
Mac
- Apple MailBuilt in. File, Import Mailboxes imports files in mbox format.
- Thunderbird with ImportExportTools NGFree. Imports MBOX messages into local mail folders.
Android
- Universal File OpenerOursLists the first 1,000 messages offline. Tap a message to read its body and attachments; Back returns to the list.
In a browser
- Universal File OpenerOursLists mailbox messages and opens their bodies and attachments locally. Nothing is uploaded. This browser reader has its own limits.
Won’t open?
Only the first 1,000 messages are listed
Our apps cap the mailbox list at 1,000 and say when more messages are present. Use a desktop email application to import the full mailbox.
Search does not find words from a body
Search in the mailbox list matches subject, sender and date. Open a message to read it, or use a mail application’s content search after import.
A Thunderbird file has no extension
Thunderbird mailbox folders can be files without a suffix. Open the message store itself, not its .msf index; make a backup before working with profile files.
A message is too large or split incorrectly
Windows refuses a single message over 16 MiB; Android’s reader limit is 24 MiB. Content-Length mailbox framing is not supported. Use the source email application to export individual EML files.
Convert an MBOX file
- To individual emailsImport into Thunderbird with ImportExportTools NG, then export the required messages as EML. Keep the original mailbox backup.
- To a mailbox in Apple MailOn a Mac, choose File, Import Mailboxes, select Files in mbox format and choose the mailbox. The imported messages appear in an Import mailbox.
MBOX files in our apps
List the first 1,000 messages in an MBOX offline on Android and Windows by subject, sender and date. Open a message to read its body and access attachments, without connecting an email account.
All Android tools and limits for MBOX files
- Lists the first 1,000 messages offline. Tap a message to read its body and attachments; Back returns to the list.
Limits
- The list stops at 1,000 messages and reports when more are present. Its search matches subject, sender and date.
- Reads mboxo and mboxrd. Content-Length framing from mboxcl is not used. The mailbox stays read-only.
- A single message is limited to 24 MiB on Android and 16 MiB on Windows.