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Univik Online MBOX Viewer
100% private. Runs only on your device
Open Inbox, Sent, Drafts and Archives from any Thunderbird profile with no Thunderbird, no ImportExportTools and no import. Runs in the browser, nothing leaves your machine.
Or pick it from your device. Messages open in this tab, on your own computer, phone or tablet. Your mailbox is never uploaded.
Every folder in a Thunderbird profile is one mbox file. Copy Inbox or Sent out of the profile and this page reads it in your browser, on the machine you are using, with no account set up and no import. Nothing goes to a server.
Point the tool at the file Thunderbird itself writes. No conversion step and no add-on in between.
The usual advice is to install Thunderbird plus the ImportExportTools NG add-on and import. Here you skip all of that and read the file straight away. The one place that add-on earns its keep is making an export in the first place, as with Proton Mail through Bridge.
A Mail folder saved from a retired PC opens on today's laptop or phone. The release that wrote it does not matter: the Supernova redesign of Thunderbird 115 and 128 changed the menus, not the file layout.
Save any message as .eml or grab an attachment. Zip all of them at once, or export the list as .csv.
Short answer: take the Inbox or Sent file out of the profile folder, bring it to the device and open it on this page. Thunderbird does not have to exist on that device at all.
Paste %APPDATA%\Thunderbird\Profiles into File Explorer, open the profile and copy a file out of Mail. Load it here in Edge, Chrome or Firefox.
The profile lives under Library, which Finder hides. Use Go to Folder with the path below, copy the file and open it in Safari or Chrome.
Look in the hidden .thunderbird folder or in the snap and flatpak locations listed below. Open the file in Firefox or Chromium without setting up a second profile. Mail from Evolution, KMail, mutt or the spool has its own page.
Thunderbird for Android reads accounts, not old profile files. Send the Inbox file to the phone through a cloud folder and read it here in the browser instead.
There is no Thunderbird for ChromeOS. Copy the mail file to Drive or a USB stick and read it in Chrome on this page.
Thunderbird keeps mail in the mboxrd flavour with a few Mozilla extras. The tool understands each of them, and the same goes for Postbox mail files, which share the layout.
Every message opens with From - and a timestamp. The tool splits exactly there, so your count matches the folder pane in Thunderbird.
X-Mozilla-Status carries the read and flagged state, X-Mozilla-Keys carries your tags. Both stay in the raw headers next to Message-ID and Received, where you can read them.
Thunderbird only marks a deleted message until you compact the folder, so it is still in the file. The tool shows everything the file holds, which means those messages appear here too.
The Archives folder is split into one file per year inside Archives.sbd. Open 2019 or 2023 on its own, or pick the whole folder to load them all.
Attachments open from their own tab. HTML messages keep their inline pictures. Remote images stay blocked until you allow them.
A profile written on Windows uses CRLF, one from Linux or Mac uses LF. Both are read, so a Mail folder moved between systems keeps its full message count.
In Thunderbird open Help and then Troubleshooting Information. Click Open Folder next to Profile Folder, then go into Mail and Local Folders. IMAP accounts sit under ImapMail instead.
Copy Inbox, Sent or Archives somewhere handy, then drop it onto the box at the top of this page. Leave the .msf files behind.
Open any message and move between the Message, Plain text, Headers and Attachments tabs. Keep what you need as an .eml file or a zip of attachments.
The profile folder has a random name that ends in .default-release on current releases, or .default on older ones. Inside it, Mail is what you want.
%APPDATA%\Thunderbird\Profiles\xxxxxxxx.default-release\Mail\. Local Folders holds POP and local mail. Each IMAP account has its own folder under ImapMail\, named after the server.
Mac: ~/Library/Thunderbird/Profiles/. Linux: ~/.thunderbird/, or for the snap build ~/snap/thunderbird/common/.thunderbird/ and for flatpak ~/.var/app/org.mozilla.Thunderbird/.thunderbird/. Then Mail as above.
Inbox, Sent, Drafts, Templates, Junk, Trash and Archives are the mail, all without an extension. Each has a companion .msf, which is only an index. Subfolders are in a matching .sbd folder, and Archives.sbd holds one file per year.
The PortableApps build on a USB stick keeps its profile inside the app folder, under Data\profile\Mail\. Open those files here the same way.
An account switched to Maildir in its settings keeps one file per message under cur and new instead of one mbox. Those are not mailbox files. The default store type is still mbox, so most profiles open here as they are.
For a few messages, open the file here and save them as .eml. For a whole profile turned into PST, PDF or another format, the Univik Thunderbird Converter for Windows does that job.
Use this online page to read one Thunderbird folder from any device. Use the free Univik MBOX Viewer for Windows to open a complete profile with every subfolder in one go, search inside message text and print.
| Feature | Online Thunderbird Viewer | MBOX Viewer for Windows |
|---|---|---|
| Install needed | None, opens in the browser | 15 MB Windows setup |
| Operating system | Windows, Mac, Linux, Chromebook, iOS, Android | Windows 7 to 11 |
| Files uploaded | Never, runs on your device | Never, runs on your PC |
| Thunderbird profile | One folder at a time | Whole profile with subfolders |
| Search | Sender, subject, recipients | Message bodies too |
| Large folders | Read in pieces, multi GB files open | No size limit |
| Browser print of the open message | Direct printing | |
| Price | Free | Free |
Yes. Carry Inbox or Sent from the profile over to whichever computer or phone you like and load it on this page. The tool reads it on its own. You do not need Thunderbird, a profile or the ImportExportTools add-on on that device.
Inbox, the one with no extension. Inbox.msf is a summary index that Thunderbird rebuilds whenever it likes, and it contains none of your mail. The same goes for Sent and Sent.msf, and every other pair.
The quick way from inside Thunderbird is Help, then Troubleshooting Information, then the Open Folder button beside Profile Folder. Typing about:profiles into the address bar works as well. The paths for Windows, Mac and Linux are listed in the section above.
Because they are still there. Thunderbird only sets a deleted flag in X-Mozilla-Status and hides the message until the folder is compacted. The tool lists what the file contains, flag or no flag. Compact the folder in Thunderbird and copy the file again if you want them gone.
Yes. An IMAP account keeps a local copy of each folder under ImapMail, in a folder named after the mail server. Those files have the same layout as Local Folders. Open them the same way, keeping in mind the copy only holds what Thunderbird had synced.
Yes. The mail files are the same format on every system. Only the line endings differ and the tool reads both. Copy the file over and open it in Safari or Chrome. Nothing about the Windows origin gets in the way.
No. Your browser reads the file from your own disk and builds the list itself. There is no server behind this page and no sign in. Once the page has loaded you can go offline and it carries on reading.
Yes. Older Thunderbird releases could not grow a folder past 4 GB, but files that large and larger open here because the tool reads them in pieces rather than all at once. Give a phone a smaller folder so the browser has room.
Grab Inbox or Sent out of the profile folder and read it here, no Thunderbird and no add-on. The file stays where it is.
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