Import MBOX to Gmail: Tool for Thunderbird, Apple Mail and Takeout

Two ways to move MBOX to Gmail

Most guides for MBOX describe one manual method. Google also publishes a script on GitHub. Its description says it is for Workspace administrators who import mbox files in bulk for their users, and it needs a Google Cloud project with a service account.

Manual method

Thunderbird, an add-on and a drag

The guides we read come down to the same 3 steps. One of them warns that sent and received mail end up mixed together afterwards.

Add the Gmail account to Thunderbird
Install the ImportExportTools NG add-on and load the MBOX with it
Drag the result over to Gmail by hand

This tool

Show it the MBOX and let it work

No extra mail client to install and configure. It reads the MBOX where it is and writes to Gmail directly.

Signs in to Gmail with an app password
Does not need an add-on or an export step
Paid, with a trial, and for Windows only

Download

Which MBOX file or folder to pick for Thunderbird, Apple Mail and Google Takeout

A Thunderbird to Gmail move starts from an account folder inside the profile. An Apple Mail to Gmail move starts from an exported package, and a Takeout download holds one .mbox. The program recognizes MBOX by what is inside the file, whatever the extension. It will not open a download that is still a .zip or .tgz, and it does not read Apple's .emlx files.

Where the mail comes from	What it is on disk	What to click	What you get in Gmail
A single .mbox or .mbx file	One file	Add files	One label named after the file
Thunderbird, one mail folder	A file with no extension, next to an .msf file. Its subfolders sit in a folder called Name.sbd	Add files, then switch the file type list in the dialog to All files (.). Without that the file is not shown	That folder plus the subfolders from the .sbd next to it
Thunderbird, a whole account	A folder such as Mail\Local Folders, an account folder or an .sbd folder	Add folder	Every mail folder with its nesting. Index files (.msf) and other service files are left out
Apple Mail export	A folder named Name.mbox with a file called mbox inside, or a folder holding several of these	Add folder. Windows sees the package as a folder, so the file dialog cannot select it	One label per package. Nested packages become nested labels
Google Takeout	One .mbox file for the whole mailbox, for example All mail Including Spam and Trash.mbox	Add files	Labels rebuilt from the X-Gmail-Labels header of each message

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How to import MBOX to Gmail, step by step

Get the MBOX onto a Windows PC

Download the Email Migration Tool, then install it on a PC with 64-bit Windows 11 or 10. The program works with mail files stored on this computer, so the MBOX has to be here before anything else. Unzip a Takeout download yourself. Copy a Thunderbird profile over as a plain folder. In Apple Mail, choose Mailbox > Export Mailbox on the Mac, then copy the whole .mbox package to the PC without opening it.

Add the file or the folder in the From panel

The From panel is on the left. Click Add files for one .mbox or a Takeout file, and Add folder for a Thunderbird account folder or an Apple Mail package. The hint in the empty panel mentions Add folder for EML only. MBOX folders are taken the same way. Each source gets a row that says Reading... until its messages are counted.

Connect Gmail with an app password

In the To panel set Email service to Gmail and type the address. An address at gmail.com or googlemail.com selects the service by itself. The password field is labeled App password, and the note under it gives the reason. Gmail does not let third-party apps in with your regular password. Click How to create one and make the password on Google's page. Paste it here and press Connect. If Gmail turns down a regular password and asks for an app password, the program shows An app password is required. Test checks the connection without starting anything.

Check where the mail will go and start

After the connection, Where messages will go fills in on the right. Destination folder reads Imported plus the file name. Leave it, or switch on Merge into the mailbox folders. Press Start migration. A large job shows Day 1 of about N and a Stop button. At the end you get Migration complete and a button, Open migration log, in case you want to check the run afterwards.

Your old mail goes under a label of its own, away from today's Inbox

When you import MBOX to Gmail with this program, a decade of old mail does not bury this week's. It all sits under one top label, and what was inside a file is one level below that file's label. In Gmail this is a label. Deleting it leaves the messages in All Mail. Those two lines are the program's own hint, and they mean a label is not an undo button. Would you prefer the old structure mixed in with what you have in Gmail now? Use the merge option from step 4.

One top label, Imported, for everything from the run
Each file gets a sub-label with its name
The Inbox stays as it was by default
Old mail sorts by its original year, not by import day
Delete the label and the mail still sits in All Mail

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What this Gmail importer does with an MBOX file

Each message is sent the way the file stores it

An MBOX file already stores each message in its internet form, with headers, body, attachments and inline pictures in one piece. To import MBOX to Gmail, Email Migration Tool does not rebuild anything. It sends those bytes with two technical changes. Line endings are set to the form mail servers expect, and the >From escaping that the MBOX format adds is removed. Gmail files the message under the date from its Date header. Read, starred, replied and draft marks are carried over where the file records them. A plain .mbox with no status headers arrives marked as read.

Subfolders turn into nested labels

Thunderbird keeps subfolders in .sbd directories, and each of them becomes one of the nested labels under its parent. Nested Apple Mail packages do the same. A Takeout file is flat. It has only a list of labels written into every message, and the program sorts the mail by that list. Each message is filed once. It goes under the first of your own labels. If there is none, it goes under a system one such as Drafts, or else under Archive. A message that carried three labels in the old mailbox keeps one here, and Gmail categories are not rebuilt. Filing a copy under every one would multiply the size of the job. Tags you set in Thunderbird stay behind as well.

Keeps count of Gmail's daily IMAP allowance

Google's help page for Workspace gives 500 MB per day as the IMAP upload limit and describes a safeguard that temporarily stops IMAP uploads for a mailbox that goes over. The program treats 500 MB as the budget of the day. When the budget is spent the job pauses, and after midnight it carries on from the same message if the window is still open. This matters most for Takeout, where one file contains an entire mailbox. Before you begin, the window shows a bar, Gmail daily limit, and a line that begins Estimated time: about. By that arithmetic a 15 GB archive needs about a month. That is an estimate.

A stopped run continues without sending mail twice

Before a message goes out, the program checks whether Gmail already has it there, and skips it if so. Close the window or shut the PC down, and the next launch shows a banner, An interrupted migration can be resumed, with Resume and Not now. Your MBOX files come back into the list by themselves. Progress is kept in a log on disk, updated after every message. When only the line fails, the program retries the connection, 5 attempts back to back.

Large archives, and only the parts you choose

A file of tens of gigabytes is indexed in one pass, and mail is not loaded into memory whole. After that the Folders to migrate tree lets you untick any branch, with Select all and Clear all above it. Spam and Trash of a Takeout file are not ticked at first, and neither are Junk and Trash of a Thunderbird profile. Period narrows the job to Last 12 months, or to a range you set under Choose dates. The source is opened for reading only, and the window says so: Files are only read. Nothing in them is changed.

The app password is not saved, and the mail goes to Google only

The app password is kept out of the settings on disk, which is why you enter it again in each new session. On the PC the program runs without administrator rights. The mail goes over an encrypted connection to Google's IMAP server and to no SoftOrbits server. One request does reach us, at license activation. It carries the key, a hardware ID of the PC and the e-mail used for the purchase. This email import tool for Gmail and Microsoft 365 takes other mail formats too, and its product page names them.

How people end up holding an MBOX file

A sealed parcel on a doorstep with a zipper running across its top.

A university address is about to expire

Graduation was in June and the login ends on October 31. You ran Takeout before the deadline. Now a 9 GB download sits on the desktop, and the mailbox it came from closes soon.

A small bird carrying a letter out of the window of an old desktop computer.

Thunderbird is not coming to the new computer

Thunderbird ran on that tower for 11 years. Its profile is the only place where those letters exist, and the new laptop will not get a mail app installed at all. Somebody has to get them out before that tower goes.

A bookshelf bending under one oversized binder between thin notebooks.

The mail archive is the biggest thing on the drive

Every backup drags 40 GB of it along. Most of it has not been opened since 2019.

Three different envelopes lying in front of three doors that lead into one room.

The mail service you used no longer exists

The cable company dropped its mail service, or you moved to another one and the address went with the contract. What remains is a file, saved as MBOX by some mail app you had back then. It cannot be opened anywhere convenient, and there is nobody at the provider to ask.

Who the Import MBOX to Gmail Tool is for

Thunderbird users who now read mail in a browser

You check Gmail in a tab or on the phone, and Thunderbird is where everything older is kept. Bring it over once and the desktop client can go. For a Thunderbird profile that has to end up at Microsoft, read how to upload MBOX to Office 365.

Mac owners with an Apple Mail archive

Your archive is on a Mac, and Email Migration Tool works on Windows only. Plan for that second machine before you begin. The exported packages travel to it on a USB stick or a shared drive, and the import happens there.

People folding one Google account into another

One login from college, one from a past job hunt, one you really use. Export each spare one. Give every .mbox a clear name before you add it, because that name becomes the label in the mailbox you keep and tells you later whose mail is whose.

Before you pay: what the trial does with your MBOX

The trial reads every layout from the table above, for as long as you need it.

For each MBOX source	Trial	Licensed
Messages sent per folder	The 25 most recent	Every message
All layouts from the table	✓	✓
Where the trial messages end up	In your real Gmail, and they stay	Recognized and skipped, the remainder follows
In a Takeout file a folder means a label, so the trial sends 25 messages per label. Once the key is entered, press Move the rest. A key works on one computer.	Download	Buy now From $ 24.99

Buy now

From $ 24.99

Download

In a Takeout file a folder means a label, so the trial sends 25 messages per label. Once the key is entered, press Move the rest. A key works on one computer.

Email Migration Tool for Gmail and Office 365 - Import PST, MBOX and EML

Price

from $ 24.99 / month

Version

3.3

File Size

67.7 Mb

Last updated on

14/08/26

Trial: 25 most recent messages per folder of each MBOX source, no expiry

System Requirements

Windows 11/10/8.1/8/7 (32/64 bit)
Intel i3, AMD Ryzen 5 or above
4 GB of RAM or above
NVIDIA® GeForce® series 8 and 8M, Intel® HD Graphics 2000, Quadro FX 4800, Quadro FX 5600, AMD Radeon™ R600, Mobility Radeon™ HD 4330, Mobility FirePro™ series, Radeon™ R5 M230 or higher graphics card with up-to-date drivers
1280 × 768 screen resolution, 32-bit color
1 GB of free hard disk space or above

Frequently Asked Questions

How do I import an MBOX file into Gmail?

With a desktop program that logs in to Gmail and adds the messages one by one over IMAP. Vendors who write about this task state that Gmail does not offer a native way to import MBOX files directly. In Email Migration Tool you add the MBOX, connect Gmail and press Start migration. Which button to use depends on where the MBOX came from, and the table above lists each case.

How do I transfer my Thunderbird emails to Gmail?

Add the account folder from your Thunderbird profile with Add folder, for example Mail\Local Folders. Each mail folder in that profile is already an MBOX file, only without an extension. There is nothing to export and no add-on to install. The program does not search your PC for the profile. You browse to that folder yourself. The program leaves out messages that Thunderbird has marked as deleted but not yet removed from the file.

Can I move my Apple Mail emails to Gmail?

Yes, in 2 stages. On the Mac, select the mailboxes and choose Mailbox > Export Mailbox. Then move the exported packages to a Windows PC and add them there with Add folder. From each package the program reads the file called mbox. It does not read .emlx files or the table_of_contents file, and it cannot work from the live Mail folders on a Mac.

Does Google Takeout work for emails?

Takeout works for getting mail out. The export is one .mbox file for the entire account, inside a .zip or .tgz download that you unzip first. Putting that file into a different account is the half Takeout leaves to you, and this program covers it. It knows a Takeout file by the label lists in its first 20 messages. System labels such as Inbox and Sent are recognized by their English names. If the export was made in another language, those labels arrive under their own names and no mail is lost.

Can I transfer all my emails to Gmail?

All the mail that is in the MBOX, with a short list of exceptions. Gmail refuses a message over its size limit, and the program skips it and puts it in the report. What an MBOX never held, contacts and a calendar, cannot come out of it, and mail filters are not moved. Mail kept in Outlook is stored in a different kind of file, and a separate page explains how to transfer Outlook emails to Gmail.

How can I extract emails from an MBOX file?

Email Migration Tool moves them into a mailbox, and from then on you read and search them in Gmail. It does not save messages out of an MBOX as separate files.

Will the imported mail show in my Inbox?

No. It shows under the Imported label and in All Mail. That holds for mail that sat in the Inbox of the old account too: it arrives as Imported, then the file name, then Inbox. With the merge option ticked, the program is built to map that old Inbox to the Inbox of the mailbox instead. Try that on one folder with the trial before a full run.

Where do I get the Gmail app password?

In your Google Account. The link How to create one in the To panel opens Google's help page with the steps. There is no Sign in with Google button in the program, and the regular password is refused. A work or school address is a different case. The program's message says Google Workspace accounts cannot create app passwords, so this version cannot connect such a mailbox. Take care with typing. After two rejected sign-ins in a row the program warns that more attempts can get your IP address blocked for up to 24 hours.

Import MBOX to Gmail from Thunderbird, Apple Mail or Google Takeout