Arca Mail Backup: Your Email Backed Up as MBOX, on Mac and Windows

Most people who arrive at this site already have an MBOX file. They exported it from Google Takeout, found it in an old Thunderbird profile, or inherited it on a USB stick, and now they want to read it. Mbox Viewer was built for that moment.

There is an earlier moment, though, and it is the one that decides whether the file exists at all: the day you make the copy. That is what Arca Mail Backup is for. It is our new app, it is out for Mac and Windows, and it does one thing: it keeps an up-to-date copy of your email on storage you own.

What it does

You connect an account, choose where the copy goes, and Arca backs it up in the background on a schedule. If it is interrupted — the laptop goes to sleep, the Wi-Fi drops — it picks up where it left off on the next run.

It works with the mail most people actually have:

• Any IMAP account: your hosting, your internet provider, cPanel, Dovecot…
• Gmail and Google Workspace, with an app password (the account needs 2-Step Verification). Gmail is copied from All Mail with its labels, so nothing is saved twice; Trash is included and Spam is optional.
• Outlook.com, Hotmail and Microsoft 365, by signing in with Microsoft.

It backs up email only: calendars and contacts are not included.

The part that matters: deletions don’t follow you

An IMAP mailbox synchronises, and synchronising is the opposite of keeping a history: delete a message on your phone and it disappears everywhere. A backup that mirrors the server inherits that problem.

Arca doesn’t mirror. A message deleted on the server stays in your backup, marked as deleted. You can search for it across every account — by subject, sender, recipient or text — and put it back. Restoring sends the messages to a new folder in the same account and changes nothing that is already on the server; by default only what was deleted comes back, so you don’t end up with duplicates.

Plain MBOX files, on your storage

The backup is not a proprietary database. Each destination gets standard MBOX files — one per folder and month — next to a manifest.json, a copy of the index and a README that explains how to open everything without Arca. Every message is stored byte for byte, as it arrived.

Two consequences follow. The first is that the copy outlives the app: Thunderbird, Apple Mail or Mbox Viewer can open it today and in twenty years. Opening it is the same job as opening any other MBOX, on Mac or on Windows.

The second is that past months never change once they are closed. That is exactly what versioning and Object Lock on a cloud bucket want: an old month written once and never touched again.

Where the files go is up to you. On the free plan, a folder on an internal or external disk of your computer. With Arca Pro, also a NAS, S3-compatible storage (Wasabi, Backblaze B2, Cloudflare R2, Hetzner, AWS…) or a folder synced with your cloud drive, and several destinations at once.

No server of ours in between

Arca talks to your mail provider straight from your computer and writes to the storage you chose. There is no Arca account to create, no server of ours that sees your mail and no analytics. Passwords stay in the macOS Keychain or the Windows Credential Manager, and the logs never contain the content, subjects or addresses of your messages.

It also takes in the MBOX files you already have

This is where the two apps meet from the other side. Arca imports MBOX files from Google Takeout, Apple Mail or Thunderbird as an offline account you can search, and it can restore that mail into one of your connected accounts. It is included in the free plan, and imported mailboxes don’t count towards your account limit.

So a Takeout downloaded years ago is not a dead end: you can read it with Mbox Viewer, and you can also put it back into a mailbox with Arca.

Free for one account

The free plan covers one account connected by IMAP, backed up in full to a disk of your computer, once a day. Search, checks, import and restore are always included, with no size limit.

Arca Pro adds more accounts (yearly levels of 1, 5, 10, 50 and 100, or a lifetime licence for one account), NAS and S3 destinations, several destinations at once and backups every few hours. Billing and refunds go through the store. And if Pro ends, nothing is locked or deleted: the backups you already have stay searchable and restorable.

On the way, with no dates yet: optional encryption with age, migration from one account to another, a Microsoft Graph connection for organisations that block IMAP, and Google Drive, OneDrive and Dropbox as destinations.

Where to get it

Version 1.0 came out on 12 October 2026 for Windows and on 14 October for Mac:

• Mac: in the Mac App Store, for macOS 14 or later.
• Windows: in the Microsoft Store, for Windows 10 version 1809 or later and Windows 11. At the time of writing, Arca Pro for Windows is still in review at the Microsoft Store; the free plan is already there.

The app is in English and Spanish for now. Prices, the full comparison of plans and the FAQ are on arcamailbackup.com.

If you only take one idea from this: the MBOX file you will one day want to open is the one you make before you need it. Arca makes it; Mbox Viewer opens it. The case for doing it with Gmail has its own article.