File Extension Guide📖 What is a DBX File?
DBX files are the mail folder files of Outlook Express. Microsoft says Outlook Express stores each mail folder as a single file with the .dbx extension, so the Inbox folder is one file named Inbox.dbx. Folders.dbx sits beside the folder files and lists the folders.
Modern Windows no longer includes Outlook Express, so old mail folder files need a viewer or a converter. The files still turn up on forgotten drives, backup discs and family computers that ran Windows XP or earlier.
One rule to remember
Copy the whole store folder before you open anything. Folders.dbx and every folder file travel together. All work happens on the copy.
🕰️ Where Did DBX Files Come From?
Outlook Express 5.0 introduced the .dbx format in 1999 and Outlook Express 6.0 kept it until Windows XP was replaced. The timeline lists each release.
Outlook Express 4.0 shipped with Windows 98 and kept mail in .mbx files, a layout similar to the Unix mbox format.
Outlook Express 5.0 arrived with Windows 98 Second Edition and switched to .dbx files, one file for each mail folder.
Outlook Express 6.0 shipped with Windows XP in October 2001 and kept the .dbx layout.
Windows Vista replaced Outlook Express with Windows Mail, so later Windows versions ship without the program. The guide Windows Mail vs Windows Live Mail vs Outlook Express compares the three.
🗃️ Which Files Sit in an Outlook Express DBX Store?
An Outlook Express store is a folder of .dbx files plus an address book. Folders.dbx, one file per mail folder and a separate .wab file are the parts you will meet.
Folders.dbx
Index of the store. This file points to the other folder files and holds no messages.
Copy it with every folder fileInbox.dbx
The Inbox folder as one file, as Microsoft describes.
One folder in one fileSent Items.dbx and other default folders
Outbox, Deleted Items and Drafts follow the same rule of one file for each folder.
Sent Items.dbxCustom folder files
Every folder you created in Outlook Express is stored as its own .dbx file.
One file per custom folderAddress book (.wab)
The Windows Address Book is a separate .wab file and not part of any .dbx file. Copy it as well.
Separate .wab file📍 Where do You Find the DBX Files?
Outlook Express shows the location itself. Microsoft says the store folder appears under Tools, Options, Maintenance and Store Folder. Microsoft also advises copying the entire store folder. On a drive without the program, search for Folders.dbx and use the folder around it as the store.
- Search for Folders.dbx. Turn on hidden files in Windows first, because the .dbx and .wab files may not show otherwise.
- Copy the whole folder. Put the copy on a second drive and leave the original untouched.
- Clear the Read Only mark. Files copied from a CD or a DVD often keep it. Clear it in the folder Properties.
- Sort by size. Write down any .dbx file near 2 GB, because Outlook Express supports files under 2 GB only.
🧪 How do You Check a DBX File?
A hex viewer shows the first bytes of a .dbx file. Open a copy and compare the bytes with the signature table: CF AD 12 FE at offset 0 and C5 or C6 at offset 4.
offset 0 CF AD 12 FE # signature of every Outlook Express mail file
offset 4 C5 # message folder such as Inbox.dbx
offset 4 C6 # folder list, Folders.dbx
A faster check needs no tools. Open one file in the online DBX viewer and read a few messages. The viewer shows whether the file holds real mail before any import starts.
⚠️ Why Does a Large DBX File Fail to Open?
Outlook Express supports files under 2 GB. Performance drops as a folder file approaches that size. Old stores could also corrupt as folders grew, so a big Inbox.dbx is the first file to inspect. The DBX converter page names the same 2 GB limit and says an oversized file often will not open in the old program.
- Copy first. Never run a repair or compaction on your only copy.
- Read it elsewhere. Open the copy in the online viewer to see how many messages the file still shows.
- Convert it. A tool that reads .dbx files directly does not depend on Outlook Express opening the file.
🔓 How do You Open a DBX File Today?
Online viewer
The online DBX viewer reads one file in your browser and needs no Outlook Express. Use it to read mail and to download single messages as EML.
Univik DBX Converter
Univik DBX Converter reads the store folder and saves PST, EML, MBOX, MSG or PDF files. A whole store converts in one batch with no Outlook Express installed.
Microsoft route into Outlook
Microsoft documents an import from Outlook Express to Outlook. On a second PC you point Outlook Express at the copied store folder and run the import wizard.
Foxmail Import menu
Foxmail 7.2 lists Outlook Express Account... as the last of seven Import entries. Import Outlook Express to Foxmail explains what to check on a copy first.
⚔️ How does DBX Compare With Other Mail Formats?
| Format | Made by | Layout | Opens in |
|---|---|---|---|
| .dbx | Outlook Express 5 and 6 | One mail folder per file | Outlook Express and the Univik viewer and converter |
| .eml | Single messages saved from a mail program | One message per file | Most mail programs, see the EML file guide |
| .pst | Outlook | Many folders in one file | Outlook, see the PST file guide |
📝 Summary
- .dbx holds one Outlook Express mail folder
- Folders.dbx lists the folders and holds no mail
- Files stay under 2 GB in Outlook Express
- The .wab address book is a separate file
- Signature CF AD 12 FE starts every file
- Copy the whole store folder before any work
- The online viewer reads one file in your browser
- The Univik converter saves PST, EML, MBOX, MSG or PDF
Last updated 22 October 2026. The one-file-per-folder rule and the store folder path come from Microsoft support. Version history and the 2 GB limit are public product history of Outlook Express.
❓ Frequently Asked Questions
A .dbx file stores one mail folder of Outlook Express. Microsoft says Outlook Express keeps each mail folder as a single file, so the Inbox folder is Inbox.dbx. Outlook Express 5.0 introduced the format in 1999 and version 6.0 shipped with Windows XP in October 2001.
Folders.dbx is the folder list of an Outlook Express store. The file points to the other folder files and holds no messages. Copy it together with the folder files, because a missing copy can hide some folder names.
DBX files sit in the store folder of the Outlook Express identity. Outlook Express shows that folder under Tools, Options, Maintenance and Store Folder. On a drive without the program, search for Folders.dbx and use the folder around it.
Outlook Express supports .dbx files under 2 GB, so a larger Inbox.dbx often fails to open. Copy the file first, read it in the online DBX viewer and convert it with a tool that does not depend on Outlook Express.
Outlook does not open a .dbx file by double click. Microsoft documents an import route from Outlook Express to Outlook that starts from the copied store folder. Converting the .dbx files to PST is the other route.
Open it in the online DBX viewer in a browser or convert it with Univik DBX Converter. The converter saves PST, EML, MBOX, MSG or PDF files and needs no Outlook Express on the PC.
A DBX file starts with the bytes CF AD 12 FE. The byte at offset 4 reads C5 for a message folder and C6 for Folders.dbx. Check the bytes on a copy in a hex viewer.
Point Univik DBX Converter at the copied store folder and choose PST, EML, MBOX, MSG or PDF. Every mail folder converts in one run and Outlook Express is not needed.
No, Outlook Express keeps the address book in a separate .wab file. Copy the .wab file together with the store folder.
No, Outlook Express stopped shipping with Windows after Windows XP and Windows Vista replaced it with Windows Mail. Old .dbx files need a viewer or a converter on current Windows.