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Understand data file storage in Outlook 2007 Roaming and Local folders

Microsoft Outlook 2007 has several data and customization files, making it easy to forget which files do what. Get an explanation of the various files within Outlook 2007's Roaming and Local folders and learn how they're used.

Microsoft Outlook 2007 stores data in a few different folders, including the Roaming and Local folders. Because these folders are similar, administrators can get confused about their purposes. Microsoft Exchange Server expert Brien Posey explains which Outlook 2007 data files are stored in the Roaming and Local folders and gives details on each folder's purpose.

File types stored in Outlook 2007's Roaming folder

Outlook 2007 is part of the Microsoft Office 2007 suite; therefore, Outlook customization files are stored at other levels of the Roaming folder. All Office products share some of a system's tools and functions. For example, all Microsoft Office products share a common dictionary that is used to spellcheck documents. According to Microsoft's documentation, dictionary customization files are stored as .DIC files within the \Roaming\Microsoft\Proof folder. However, on my system, these files were stored in the \Roaming\Microsoft\UProof folder.

Outlook 2007 uses a few other miscellaneous types of shared files. Outlook stores stationary as .HTM files in the \Roaming\Microsoft\Stationary folder. Template files are also stored in a shared location. But these files exist as .OFT files in the \Roaming\Microsoft\Templates folder.

More information on Microsoft Outlook 2007:
How to copy and transfer a Microsoft Outlook 2007 auto fill list

Accessing SharePoint calendars through Microsoft Outlook 2007

One profile-specific component that's stored outside of the main \Roaming\Microsoft\Outlook folder is the signature file. Because Outlook users can highly customize their signatures, there are a variety of file types that can be used as part of the signature file. These file types include .RTF, .HTM and .TXT files, which are stored in the \Roaming\Microsoft\Signatures folder.

File types stored in Outlook 2007's Local folder

The user profile folder contains an \AppData\Roaming folder as well as an \AppData\Local folder. The \Local folder is simpler than the \Roaming folder for several reasons. There are only four types of files stored in the \Local portion of the profile, all of which are stored in

All the Microsoft Outlook file types:

 the same location: \Users\user name\AppData\Local\Microsoft\Outlook. Most files located here are profile specific, but the file name makes it easy to determine to which profile a file belongs.

  1. The .PST file is probably the best known type of Outlook data file. .PST files allow users to create folders, contact lists and more. These folders, however, remain separate from the Exchange information store. .PST files are typically used for long-term archival or data portability.

  3. The .OST file is Outlook's offline cache file. If cached mode is enabled for a user's mailbox, all mailbox contents are copied to this file. This allows the user to access the mailbox when working offline. More importantly, the .OST file is directly tied to the user's mailbox. If the Outlook profile is altered so that it connects to a different mailbox, the .OST file is rendered invalid -- even if the new mailbox has the same name as the old one.

  5. The .Sharing.XML.OBI file keeps track of RSS feeds to which the user is subscribed.

  7. The Extend.dat file keeps track of add-ons that have been integrated into Outlook. If this file is destroyed, Outlook will automatically regenerate it.

About the author: Brien M. Posey, MCSE, is a five-time recipient of Microsoft's Most Valuable Professional (MVP) award for his work with Exchange Server, Windows Server, Internet Information Services (IIS), and File Systems and Storage. Brien has served as CIO for a nationwide chain of hospitals and was once responsible for the Department of Information Management at Fort Knox. As a freelance technical writer, Brien has written for Microsoft, TechTarget, CNET, ZDNet, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal website at

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