Free EML to MBOX converter
Combine loose .eml files into a single .mbox mailbox — ready to import into Thunderbird, Apple Mail, or any client that speaks mbox.
- 100% in your browser — never uploaded
- Valid mboxrd, import-ready
- Free, no signup
No .eml files handy?
How it works
From loose files to an importable mailbox
01
Collect your .eml files
Saved messages from Gmail, Apple Mail, Thunderbird, or an email backup — drop them all in at once.
02
Joined in your browser
Each message gets a proper mbox “From ” envelope line built from its sender and date — nothing leaves your device.
03
Download & import
One .mbox file, ready for Thunderbird's ImportExportTools NG, Apple Mail's importer, or your archive.
When do you need .eml → mbox?
Mail clients rarely import loose .eml files in bulk — but nearly all of them import mbox. So whenever a folder of saved messages needs to become a real mailbox again — moving an archive into Thunderbird, restoring messages into Apple Mail, or consolidating years of scattered exports into one file — you convert to mbox first. This tool does the joining; your mail client does the importing.
FAQ
What is an mbox file?
mbox is the classic Unix mailbox format: an entire folder of email concatenated into one file, each message preceded by a “From ” separator line. It's the lingua franca for moving mail between clients — Thunderbird, Apple Mail, and most archive tools can import it.
How do I import the .mbox into Thunderbird?
Install the ImportExportTools NG add-on, then right-click a folder → ImportExportTools NG → Import mbox file, and pick the file you downloaded here. Your messages appear as a normal folder.
How do I import it into Apple Mail?
In Apple Mail choose File → Import Mailboxes…, select “Files in mbox format”, and point it at the downloaded .mbox. The messages land in an “Import” mailbox you can drag anywhere.
What order will the messages be in?
If every .eml has a parseable Date header, messages are sorted oldest-first — the order mail clients expect. If any date is missing or unreadable, the mbox keeps the exact order you added the files in. The list on this page always shows the order that will be exported.
Is anything uploaded when I combine my emails here?
No. The files are read and joined by JavaScript running locally in your browser and never leave your device. The .mbox download is generated locally too.
Can I convert back from mbox to .eml later?
Yes — the conversion is lossless in both directions. Our MBOX to EML converter splits any mbox (including the one you build here) back into individual .eml files, so you can round-trip freely.
Going the other way? Split a mailbox back into single messages with the MBOX to EML converter, or browse any mbox without importing it in the free MBOX viewer. Unsure what's inside a .eml file? Read our guide to the format. And if you're consolidating exports to finally sort out your backups, start with every email backup method, compared. Importing the result into Thunderbird? See how to back up Thunderbird emails for keeping that archive safe afterwards.