How to gather all the email on your computer into one archive

By Michael, founder of EmailAttic · October 2026 · 9 min read

To gather all the email on your computer, find every file that holds mail — Outlook PST and OST files, Thunderbird mailbox files, Windows Live Mail folders of .eml messages, loose .msg files, Google Takeout zips and any old backups — then merge them into one archive with the duplicates removed and each mailbox kept separate. You can do that by hand with a file search and a lot of patience, or point EmailAttic at the drive and let it find, sort and de-duplicate everything in one run, with nothing leaving your computer. This guide covers both.

Where email hides on a Windows PC

Email does not live in one place. Every program that ever downloaded it kept its own copy in its own folder, in its own format, and most of those folders are hidden by default. These are the places to look.

Outlook: PST and OST files

Outlook 2010 and later keep your mail in C:\Users\<you>\Documents\Outlook Files\ as .pst files. The offline copy of an Exchange, Microsoft 365 or IMAP account is an .ost file in C:\Users\<you>\AppData\Local\Microsoft\Outlook\, which is also where older Outlook versions put their .pst files and where AutoArchive leaves archive.pst. On an XP-era drive the same folder is Documents and Settings\<you>\Local Settings\Application Data\Microsoft\Outlook\. People also saved PSTs by hand anywhere at all — mail2009.pst on the Desktop, backup-old.pst on a USB stick. If you have a drawer of these, see how to open old PST files without Outlook.

Thunderbird: mailbox files with no extension

Thunderbird keeps everything in a profile folder under C:\Users\<you>\AppData\Roaming\Thunderbird\Profiles\<name>.default\, in Mail\Local Folders\ for local mail and ImapMail\<server>\ for each account. The mailbox files are plain MBOX, but they are named Inbox, Sent, Archives with no extension at all; the .msf file next to each one is only an index. A search for *.mbox finds none of them.

Windows Live Mail and Windows Mail: folders of .eml files

Windows Live Mail stored one .eml file per message under C:\Users\<you>\AppData\Local\Microsoft\Windows Live Mail\, one subfolder per account and one below that per mail folder. Windows Mail on Vista did the same under AppData\Local\Microsoft\Windows Mail\Local Folders\. Tens of thousands of small files, which is exactly why nobody ever copied them anywhere.

Loose .msg files saved to disk

Every time someone dragged a message out of Outlook into a folder, Outlook wrote a .msg file. They turn up in project folders, on the Desktop, in Documents, inside "important" folders on old drives. Each one is a single message, often with its attachments inside, and they are rarely anywhere near the rest of the mail.

Google Takeout: an MBOX inside a zip

Gmail keeps nothing on your PC unless you exported it. A Takeout export lands in Downloads as takeout-20xx…-001.zip, often several numbered zips for a large account, and inside each is Takeout\Mail\All mail Including Spam and Trash.mbox. If you have one of these and have never opened it, see You downloaded Google Takeout — now what?

Old backups: external drives and zip, rar and 7z archives

Then there is everything that was ever backed up: the external drive from the last laptop, the one before that, the NAS folder called Backup, and the archives inside them — mail-backup.zip, outlook-2012.rar, old-pc.7z, sometimes with a password someone set fifteen years ago, sometimes a zip inside a rar inside a zip. These reliably hold the mail that exists nowhere else.

Doing it by hand

With hidden items showing, open This PC in File Explorer and type *.pst OR *.ost OR *.mbox OR *.eml OR *.msg into the search box. Explorer will walk every drive and list each file by that extension. The same search in PowerShell gives you a list you can save:

Get-ChildItem C:\ -Recurse -Force -Include *.pst,*.ost,*.mbox,*.eml,*.msg -ErrorAction SilentlyContinue | Select-Object FullName,Length

Run it once per drive, including each external drive, and you have an inventory. Copy every file it found into one folder and you have, in the narrowest sense, gathered all the email on your computer. The trouble starts when you try to use it.

Why the by-hand version stalls

• The search misses things. Thunderbird mailboxes have no extension. Backups renamed to .bak or .old do not match. Nothing inside a zip, rar or 7z is searched at all, and a Takeout export is nothing but a zip.
• Half of it is duplicates. Every backup overlaps the one before it. A 2015 PST and a 2019 PST hold most of the same mail, a Takeout export holds everything an older export did, and the same message sits in one person's Sent and another's Inbox. Pile the files together and the archive is mostly copies of itself. Removing them safely is its own job — see how to find and delete duplicate emails for why matching on subject and date is the wrong way.
• The accounts are mixed together. One folder of files from a family PC holds his mail, her mail, a shared account and a business address. A pile of PSTs does not say whose is whose; you find out by opening each one.
• The formats need different tools. PST wants Outlook, and the new Outlook will not open old PSTs at all. An OST will not open in Outlook without the account it came from. MBOX wants Thunderbird and an add-on. Password-protected archives want the password, one prompt at a time.
• You cannot tell when you are done. Nothing tells you whether every message made it, so the old drives stay in the drawer "just in case".

How EmailAttic gathers it

EmailAttic is built for exactly this job. You point it at a source — Add drive, Add folder or Add files, as many as you like, a whole C:\ and an external drive together if that is where the mail is — and click Scan my email. It walks everything you gave it and shows you every mailbox it found before reading or writing a single message. Your originals are opened read-only and never changed.

• It finds every kind of mail file. Outlook PST and OST, both the old ANSI and the Unicode generation, with no Outlook and no account needed; MBOX, including the Takeout export and Thunderbird's extensionless mailbox files; EML folders; MSG files; Maildir. Files that hide their type — .bak, .old, no extension — are recognized by their contents, not their names.
• It looks inside archives. ZIP, RAR, 7Z, TAR, TAR.GZ and single GZ, BZ2 and XZ files are unpacked automatically, archives inside archives are followed all the way down, and password-protected ZIP, RAR and 7Z archives are supported: EmailAttic asks for the password when it reaches one, and one answer can cover every protected archive the scan still meets. RAR extraction is Windows-only for now.
• It groups mail by whose mailbox it is. EmailAttic works out the account holder of each container and files that mail under that person, so a folder holding six people's backups becomes six mailboxes without you sorting anything. You can then give each mailbox a category you name — Business, Personal, Family — and send each category to its own folder or drive.
• It removes the duplicates. Every message is compared by Message-ID and content across every source, and one copy is kept — sent and received together, attachments intact — even when the same mailbox was backed up a dozen times.
• It writes one archive you own. The result is ordinary .eml files in ordinary folders, archive\<mailbox>\<year>\<year-month>\, readable by any mail program now and in thirty years. A report.txt next to it accounts for every message read: how many were kept, how many were duplicates, and any file that could not be opened.
• It can grow. Find another drive next year? Point EmailAttic at the same archive folder and it adds only what is new, skipping everything already there.

Once everything is gathered, the rest of the job — deciding what to keep, backing it up, re-running the pass yearly — is laid out in how to organize decades of old email, step by step.

Questions people ask

Where are my emails stored on my PC?

It depends on the program that downloaded them. Outlook keeps PST files in Documents\Outlook Files and OST files in AppData\Local\Microsoft\Outlook. Thunderbird keeps mailbox files inside AppData\Roaming\Thunderbird\Profiles. Windows Live Mail keeps one .eml file per message under AppData\Local\Microsoft\Windows Live Mail. Webmail such as Gmail keeps nothing on your PC unless you downloaded a Google Takeout export, which is a zip in your Downloads folder.

How do I find all the email files on my computer?

Turn on hidden items in File Explorer and search every drive for *.pst, *.ost, *.mbox, *.eml and *.msg. Then check two places a file search misses: the Thunderbird profile folder, whose mailbox files have no extension, and the inside of any zip, rar or 7z backup. EmailAttic does the whole search in one pass, including inside archives, and recognizes mail files by their contents rather than their names.

How do I collect all my emails in one place?

Gather every mail file you found, then merge them at the message level: remove the duplicates that every backup carries, and keep each person's mailbox separate instead of pouring everything into one pile. EmailAttic does that in one run and writes the result as ordinary .eml files in folders by mailbox and year, with a report of what was read, what was kept and what was a duplicate.

Can I open an OST file without Outlook?

Not with Outlook itself. An OST is Outlook's offline copy of a server mailbox, and Outlook will not open one that is not attached to the original account. EmailAttic reads OST files directly, with no Outlook and no account needed, so the mail on a dead laptop's OST becomes part of the archive like any other file.