Outlook 2016 cannot open OST file

All of a sudden when I try to open Outlook I get an error message that it cannot open the OST file and when I click OK the error message closes without opening the app.  I tried follow other instructions for earlier versions - for example deleting the OST file reference. But when I try to open again the file is recreated but still cannot be opened (get the error message again). As far as I know between the last access to Outlook and now, no changes or updates were made to my Office programs.

UPDATE: On reboot, Outlook now opens and shows my email/Exchange account (an outlook.com address) but does not find any emails.  When checking the folder with OST files, I see a new file was created (*** Email address is removed for privacy ***(3).ost) which is much smaller than the two previous filed created over two months ago. The previous 2 versions were about 170 MB, and this one created today - appended (3) - is only about 16 MB. 

 

Question Info


Last updated October 21, 2019 Views 64,538 Applies to:

Hi John,

Thank you for posting your query on Microsoft Office Community.

 

Before we proceed, I need more information to help you better.

 

You have mentioned in the query that it is an Exchange Account, and you also stated that it’s an Outlook.com account, kindly let us know that how’s the account set up?

 

What is the type of account? Is it a POP, IMAP, Exchange ActiveSync or Exchange account?

 

From the issue description it looks like there are duplicate accounts created in Outlook 2016, due to that you have issue with send and receive issue.

 

Let’s delete the duplicate account by following suggestions from the below article and check if it helps.

https://support.office.com/en-in/article/Remove-an-email-account-from-Outlook-1fa900ae-6dc8-468c-b754-10292f7ee47a

 

Try the suggestions and let us know the result at your earliest convenience.

Thank you.

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I only have one account set up with Outlook 2016, and it is an Exchange ActiveSync account for my Outlook email address. There are no duplicates.

I tried to delete the account and add it again. I get this error:

"Before deleting the e-mail account containing your person mail, contacts, and calendar data, you must create a new location for your data." I did not complete this step.

By the way, since I have gotten the OST error and rebooted, the email account shows up in Outlook (which will now open without error), but there are no emails, no contacts, and the calendar is empty. 

Also in my folder AppData/Local/Microsoft/Outlook I have the following files:

*** Email address is removed for privacy ***       8.17.2015

*** Email address is removed for privacy ***(2).ost   8.17.2015

*** Email address is removed for privacy ***(3).ost  10.19.2015

Using Outlook online (browser) all my email and contacts and calendar show up.

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UPDATE:

Since I could not delete OST file using the above linked steps, I decided to try and simply delete every existing OST file by going directly to the folder and deleting them.

That worked. Outlook when opened regenerated the OST file. It took a while, but finally all email and folders as well as contacts and calendar data are now appearing again. This includes emails I sent today using the browser version of Outlook.

NOTE: The application regenerated the file *******Email ID removed for PII*******  ost and not the file *******Email ID removed for PII******* (without the 3).  Can you confirm that will not cause problems in the future?

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What is the type of account? Is it a POP, IMAP, Exchange ActiveSync or Exchange account?

I got an IMAP account, and this additional problem: Before it happened, I had some subfolders that outlook stated only was saved on the computer. These are now gone. I assume that they are in the original ost-file on the computer, which has a bigger file-size than the new ***(2).ost file. But how can I open the original file to copy the emails over to the new ost-file ?

I have tried opening the ost-file in outlook by going File > Account Settings > Account Settings > Data Files > Add, but it only allows to open pst-files that way. 

What to do ?

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Here is what I found when I encountered this.   I tried a lot of the same steps, but had run into the same thing where it started a whole new file every time it hung up.    Then I got curious and tried the following when encountered on the same "outlook.com" account.

1) I closed all processess for Outlook.exe through the task manager.   Half the time, even though it looked like Outlook had just closed itself, it still had the outlook.exe process running in the background.

2) Ran a repair on the OST using the scanpst.exe tool found in the "C:\Program Files\Microsoft Office\root\Office16" folder on the OST.

3) KEY TRICK -> Deleted the affiliated @outlook.com.ost.tmp found in the Data File folder.  For mine, it was:
"C:\Users\{user name}\AppData\Local\Microsoft\Outlook"


Once the TMP file was gone, Outlook 2016 stopped having an issue.   So, apparently it was both the ".ost.tmp" and the ".ost" that became corrupted.  By deleting the tmp and repairing the ost, everything went back to normal without it trying to create a new ost file to work with.

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Thanks for the details. It worked! As you said, the trick in step#3 is very important, otherwise same error reports. In my case, I renamed the tmp file with a .backup extension instead of deleting. Also the temp file name starts with ~{user name}.

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