Problem solve Get help with specific problems with your technologies, process and projects.

Cleaning up Microsoft Outlook after a dial-tone database restore

Performing a dial-tone Exchange Server database restore can be a convenient way to get users up and running quickly in a disaster, but its use requires post-recovery cleanup to .OST files in Microsoft Outlook.

Please let others know how useful this tip is via the rating scale at the end of it. Do you have a useful Exchange or Outlook tip, timesaver or workaround to share? Submit it to our tip contest and you could win a prize.

A couple of months ago, I had a catastrophic Exchange Server failure and had to rebuild my server from scratch. During the course of rebuilding the server, I discovered that my most recent backup had also been destroyed in the disaster. Since I needed to be able to send and receive e-mail immediately, I was forced to perform a dial-tone restore.

A dial-tone restore is a procedure in which you create empty mailboxes so users can begin sending and receiving new e-mail while you're restoring the lost data.

I would have greatly preferred to perform a normal Exchange restoration procedure, but in this particular case, I went with the dial-tone method out of necessity. To make a long story short, I was able to restore my data by extracting it from Microsoft Outlook's offline cache and then placing it into a .PST file. I then merged the contents of the .PST file with my new mailbox and I was back in business.

Well, almost….

There was one lingering issue. After the dial-tone restore, every time I opened Outlook, I would see a message telling me that Microsoft Exchange is running in recovery mode. The dialog box would then give me a choice of either connecting to Exchange Server or working offline.

The message related to the way Microsoft Outlook caches messages. Outlook maintains a cached copy of all messages, so if Exchange ever goes down, you still have access to your old messages -- although you won't be able to receive new messages until the server comes back up.

Outlook stores the cached messages in an .OST file. The .OST file is encrypted and linked to a specific mailbox. When you perform a dial-tone restore, you are creating a new mailbox, even though the new mailbox has the same name as the old one.

The problem: Outlook is still linking the cache file to the old mailbox. Hence, the prompt asking if you want to connect to Exchange Server or work offline.

If you choose to connect to the Exchange server, you will have access to your Exchange mailbox -- but not to your offline cache. If you choose to work offline, you will have access to your cache -- but not to your Exchange mailbox. This is actually a safety feature that's unique to Outlook 2003. Older versions of Outlook would simply lock you out of your cached files.

In my particular case though, I got everything I needed out of my cache and merged it with my Exchange mailbox. I therefore needed to do away with the old cache and create a new one, so the "Exchange is in recovery mode" message would go away.

Removing an old .OST file and creating a new one

Before I show you how to get rid of an old .OST file and establish a new one, I recommend that you make a full system backup in case anything goes wrong. I also strongly suggest you take one last look to make sure you've gotten everything you need out of your offline cache. Once you perform the following procedure, you won't get another chance.

  1. Open Outlook and connect to Exchange Server.

  2. When Outlook opens, select Tools -> E-Mail Accounts.

  3. Select the "View or Change Existing E-Mail Accounts" option and click Next.

  4. On the following screen, select the Microsoft Exchange Server account and then click the Change button, then More Settings.

  5. Click the Advanced tab and clear the "Use Cached Exchange Mode" checkbox.

  6. Now click Apply. (For some reason a glitch in Outlook sometimes invalidates the change if you simply click OK.)

  7. Upon clicking Apply, you will see a dialog box appear indicating that you must restart Microsoft Outlook for the changes to take effect. Click OK to clear the message, but do not restart Outlook.

  8. Click the Offline Folder File Settings button.

  9. When the Offline Folder File Settings dialog box appears, click the Disable Offline Use button.

  10. You will see a message telling you that your existing .OST file is about to be deleted from your profile and rendered useless. Take a deep breath, fasten your seatbelt, and click Yes to permit the operation.

  11. Click OK, Next, and Finish, to close the remaining dialog boxes.

  12. Close and reopen Outlook.

You'll notice that the message about Exchange being in recovery mode is gone. We aren't done quite yet though. Cache mode is still disabled, which means that if Exchange goes down, you won't have access to any of your data until the server comes back up.

Re-enabling cache mode

  1. In Outlook, go to Tools -> E-Mail Accounts.

  2. Select the "View or Change Existing E-Mail Accounts" option and click Next.

  3. Highlight the Microsoft Exchange Server account from the list and click the Change button, followed by More Settings.

  4. Select the Advanced tab and then mark off the "Use Cached Exchange Mode" checkbox.

  5. Next, click the Offline Folder File Settings button. Your old .OST file will be listed, but you can't use it. Therefore, type in a name for a new .OST file and click OK.

  6. You will now see a message telling you that the .OST file you've specified cannot be found. When asked if you would like to create it, click Yes to create a new .OST file.

  7. Click OK and you will see a message telling you that you need to restart Outlook. Click OK to clear the message, then click Next, followed by Finish to complete the process.

  8. Now just restart Outlook and you should be in business.

About the author: Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Exchange Server, and has previously received Microsoft's MVP award for Windows Server and Internet Information Server (IIS). 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 Web site at

Do you have comments on this tip? Let us know.
Related information from

  • Tip: Faster Exchange Server recovery with the Dial Tone Method
  • Tip: Recovering Exchange Server from .OST files
  • 10 tips in 10 minutes: Fundamentals of Exchange Server backup and recovery
  • Best Practices Checklist: Exchange Server disaster recovery planning
  • Reference Center: Microsoft Outlook tips and resources
  • Reference Center: Exchange Server backup and recovery tips and resources

  • Dig Deeper on Outlook management

    Start the conversation

    Send me notifications when other members comment.

    Please create a username to comment.