I have a quite big problem with customer's MS Exchange.

The server got it's disk filled about 2 weeks ago, so it's currently offline. They plan to upgrade it, but not in hurry, as they use it mainly for OWA and back-up - the mails exchange is done via SMTP and POP3.

Trying to diagnose some problem today, one of the users has (following the ISP instructions), removed the Exchange account from Outlook, which essentially left the OST orphaned.

The user naturally didn't move the emails or any other data to the Archive / PST before, so these emails located on the OST only.

So currently I'm trying to figure out how to restore them. There are 2 options:

1) Make the user buy some tool to convert them to PST, and import as archive / main Outlok file?

2) Reconnect the Outlook to Exchange (once it up), let it sync the old server content, then shutdown Outlook and replace the new OST with the old one, start Outlook again in offline mode and move these files to archive.

3) Any other method?

Can someone advice what would be the best approach here? The used versions are Outlook 2007 and Exchange 2003.



I'm confused. You say that "the mails exchange is done via SMTP and POP3", so does that mean that the users were connecting to Exchange via POP? If so, then there should be no ost file, there should be a pst file. If they were connecting to Exchange via MAPI and there is in fact an ost file, then the emails will still be in the mailbox on the server as the ost file is simply an "offline" copy of the mailbox. Emails are not downloaded to the ost file and deleted from the server like they are when using POP. Is the server down hard? If not, then simply create a new Outlook profile to connect to Exchange via MAPI and get on with your day. If the server is down hard, then you will need to use a third party utility to recover the emails from the ost file.


  • The users worked with another Exchange server located in HQ, their local Exchange server was mainly for OWA and backup. – SyRenity Mar 24 '10 at 12:52
  • So the Exchange server where their mailboxes exist is still up and running? If so, then create a new Outlook profile to connect to the mailbox server and forget about the current ost file, Outlook will create a new ost file. As I said, the ost file is merely a local copy of the mailbox, all of the emails still exist in the mailboxes on the mailbox server. – joeqwerty Mar 24 '10 at 13:44
  • That's the point - it's running but the mail store is offline, because there is no space available. Therefore there are quite a lot of emails that stored only on Outlook OST. – SyRenity Mar 24 '10 at 15:10
  • @joeqwerty: Pretty mind-bending, isn't it? They're using Exchange as a glorified PST file! >smile< – Evan Anderson Mar 24 '10 at 15:16
  • @Evan: LOL. @syrenity: It seems you're trying to fix a symptom of the problem instead of the problem itself. Have you looked at getting the problem on the server resolved so that you can bring the mailstores back on line? – joeqwerty Mar 24 '10 at 16:00

Googling around gave me this site, whose utility may help. Backup the file first though...

  • Thanks, but it works only with Outlook 2002 and lower. – SyRenity Mar 24 '10 at 12:08


I misunderstood your situation (hey, everybody-- read the prior edit to see how I can look dumb!) in my initial reading.

I'd try method #2 first, as you've got nothing to lose by trying it. I don't think it's going to work, but it's worth a shot.

Would you have a backup of the user's registry somewhere prior to their removal of the Exchange account from the MAPI profile? You could restore that (or just the "HKCU\Software\Microsoft\Windows NT\Windows Messaging Subsystem" subtree, where the MAPI profile is kept) and then the existing OST should "come to life" again.

  • They are not visible in Outlook as the user removed the Exchange account without moving the emails to PST as he should have. – SyRenity Mar 24 '10 at 11:46
  • Ahhh... I misunderstood, then. Silly me. – Evan Anderson Mar 24 '10 at 12:06

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