Outlook 2016 - frequent .ost corruption

This spring, I updated all of our users to Win10 and Office 2016 (from Win7/Office 2010).  These were clean installs, not upgrades.  Ever since, a number of users have had frequent occurrences of their .ost files becoming corrupted.  (Outlook can't open, saying that it can't open the .ost file.)  If I just delete the .ost, Outlook crashes on next start-up.  I have to delete it, then completely reboot the machine before it will finally let me re-open Outlook.

I've tried re-creating profiles, looking for add-ons to disable (there aren't any), starting it in safe mode, etc... nothing works except deleting the ost and rebooting.  And then the issue often just comes back later (usually the next time they go to restart Outlook).  We're running Exchange Online through O365, but everyone uses regular Outlook 2016 desktop client for access, which is where the problem lies.  We never had these issues with the same server when people were using Win7/Office 2010, and now I'm getting at least a few a week.

I've seen some other people talking about the same or similar issues, but I haven't seen any real resolutions (just the workaround of deleting the .ost).  This isn't a fix - especially for those of us that have limited bandwidth.  It's quite detrimental to our operation to have a few gigs of email re-downloading every day.  If anyone has any suggestions of where to look to try to track down a real cause/solution for this, I'd be very appreciative.

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Hi Awalters.cawast.org,

Regarding “Outlook can't open, saying that it can't open the .ost file.” ,do you mean that you receive an error “Cannot start Microsoft Office Outlook. Cannot open the Outlook Window”? if yes, follow this link to fix this error. Let me know if it  is a different error.

Based on your description, I would like you to follow the steps below to narrow down the issue:

1. To check if this issue is related to exchange cache, uncheck the cached exchange mode on the email account (File > Account settings > Account settings > E-mail tab > double click the email account > uncheck “Use Cached Exchange Mode”.)

 

2. To check if the issue is related to mailbox size,  Login to OWA, and try to archive your inbox, then check if the profile works on the Outlook client

3. Run the /resetnavpane command (close Outlook > Start > Run > on the space, type Outlook.exe /resetnavpane .

If you still experience the issue, please follow the steps and provide the following information to further troubleshoot:

1. Run Online Repair.  

2. Run SARA for Office 365.   

3. Screenshot of “Outlook can't open, saying that it can't open the .ost file.”

Looking forward to you updates.

Best Regards,

Ruel

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The full error I get is "Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The file C:\Users\accountname\AppData\Local\Microsoft\Outlook\emailaddress.ost cannot be opened."

And yes, it's definitely related to the cache, as it's specifically the ost having the issue.  Running in non-cached mode is not an option.

I'm not certain what the issue would be with mailbox size, but the mailboxes in question are all under 5GB (and some under 1 or 2).  Surely that shouldn't cause an issue?

I ran with the resetnavpane parameter the first couple of times it happened, to no effect.

I did run an Office repair, a number of times as well - again, no effect.  I haven't yet tried the Support and Recovery Assistant - I'll try that next time one has an issue.

However, I'm less concerned about how to fix the issue when it happens, and more about why it keeps happening and what I can do to prevent it in the first place.  I saw references elsewhere that the ost can get corrupted if network connectivity is lost while Outlook is using the file.  This would certainly be consistent with the timing of the most recent wave of errors, as it happened when we had a brief network issue.  If that's true (and potentially way more likely with 2016 for some reason), that's a huge issue for us.  Network connections aren't always 100% consistent and reliable, especially in the remote locations many of our staff work on a regular basis.  The read/write process definitely needs to be more robust than to completely ruin a multi-gig file just because a network connection drops for a second or two...

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Hi Awalters.cawast.org,

Regarding the “Outlook.exe /resetnavpane” , if Outlook still won’t open after you run this command, rename (nameofprofile.xml) to nameofprofile.xml.old. To find this file, on Search/Run space, type %appdata%\Microsoft\Outlook. This is to check the “set of folders cannot be opened…” from the error you received. Also try unchecking Exchange Cached mode and see if the error still shows.

To identify the possible root cause of this problem, please wait for the result of the SARA test and provide us with the result.

I understand you have a brief network issue which results in Outlook profile corruption. If the issue occurs again, please try the following:

1.) Check this link: https://testconnectivity.microsoft.com/ and you may need to input your Office 365 user ID and password.

2.) Run the “Microsoft Office Outlook Connectivity Tests”, Under Office 365 tab.

3.) Provide us the full result log or attach the XML file via private message.

Looking forward to your updates.

Best Regards,

Ruel

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Next time it happens, I'll do this.  Thank you.

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Hi Awalters.cawast.org,

 

When the issue reoccurs and you need further help from our team ,feel free to post back.

 

Thank you,

Ruel

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It happened again, and I sent you the log.  Thank you!

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Hi Awalters.cawast.org,

Thank you for sharing with us this information. I need to do more analysis and consulting on this reoccurring issue and will reply to you once there is any update.

Thank you for your understanding and patience.

Thank you,

Ruel

[Updated by Ruel Mayoya MSFT Support, 1:40 AM, Sept, 16, 2016 (UTC)].

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Hi Awalters.cawast.org,

Do you still encounter the Outlook issue? If yes, please download and use Microsoft Office Configuration Analyzer Tool 2.2 to scan the affected Outlook, and see what it will report.

Also, please make sure that there’s no anti-virus or other security related software which may touch the OST files.

Additionally, I see that you have mentioned your network connectivity. In order to avoid missing any possibility, can you please try the affected Outlook in another network environment?

Thanks,
Allen

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Hi Awalters.cawast.org,

Got any updates which you may share with us?

Thanks,

Allen

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I'm not having the issue again at the moment, no.  When I had it, I ran the tool Ruel suggested and sent him the results.  Should I also be running this second tool and sending you those results?  This procedure is confusing.

As for network environment, I need this to work in scenarios where the network is not stable, as we have staff that travel all over the world, often to places with unreliable internet.  We cannot have it corrupting their email cache.

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Last updated March 23, 2021 Views 12,656 Applies to: