What is DBX File Format?

Technical Description of .dbx File Extension

Type of File Email folder
Application Primarily Associated Microsoft Outlook Express
Organization Microsoft
File Extension .dbx
File Signature CF AD 12 FE

What is DBX File Format: Introduction

It is a mail file format, which is utilized by a desktop-based email application i.e., Microsoft Outlook Express. The file saves a collection of each email folder. It saves emails of a specific folder on the profile of end users. A DBX file is storing multiple emails within a single folder, which involves customized folders too. For example: Outlook is having Inbox as an email folder within it, which will be having corresponding inbox.dbx file extension on local machine. If needed, all these folders can be migrated to some other location, in order to have backup of mail messages. Moreover, files had now increased their usage from Outlook Express to Windows Mail of Vista OS and Window Live Mail of Windows 7.

DBX File Location

A DBX file is the collection of emails, which are more of mail folder rather than a file. MS Outlook Express uses a common file extension in order to store emails of each of its folder. Entire user accounts folders are generated on the email program, which are located at default storage folder location in .dbx file extension. Every folder will be denoted as outbox.dbx, inbox.dbx, deleteditems.dbx, sentitems.dbx, etc.


At initial stage, file structure of DBX file format denotes a basic hexadecimal arrangement. The main header portion is considered as file signature, which will be shown at starting of hexadecimal value: CLSID, i.e., content class ID. It is an identifier that is helping in differentiating the file type of DBX. In general, it is a string type that is used to define corresponding files on the operating system.

Note: Whenever an email is deleted, the header block and data block length gets updated for reflecting deletion procedure.

Recommendation: Convert .dbx file to PST format to access Outlook Express email data into Outlook email client application.

Technical Information About DBX File

There are some specific functions, which are stored along with DBX files at time of saving all emails and updating system settings. These particular functions are mentioned below:

Mail folder.dbx: Every individual folder of Outlook Express is having file with .dbx extension.

Folders.dbx: It indicates index of complete Outlook Express files. These files are further recorded in formatting of entire folder, which is somewhat similar to MBR.

Inbox.dbx: It is the default email folder of every email clients like Outlook Express. This is having functioning of regenaration and if this file gets deleted then, automatically Microsoft application create it, automatically. There are some other DBX files related to it i.e., outbox.dbx, draft.dbx, deleted.dbx, and sent.dbx.

POP3uidl.dbx: It is a collection of pop3uidl letter information. For example: entire parameters of the server letter will be received and one, which is not having letter will be reserved.

Offline.dbx: Basically, it is for email account that are configured with IMAP configuration

News group name.dbx: It is quite similar as other folders and each news group is saved as .dbx file.


Both professional and home users operates Microsoft Outlook Express like a comprehensible email program. It stores all the mailboxes data in DBX file format therefore, it is mandatory for such end users to have knowledge about this file. In this blog, one is going to know what is DBX file extension along with its structure and technicalities.