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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.
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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.
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
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 http://www.brienposey.com.
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Related information from SearchExchange.com:
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
