How to open someone's OST

We use Exchange OnLine and Outlook 2013. One of coworker left the company, so his account was deleted from Exchange. I have a copy of his ost file. How can I convert his OST to PST, so that my company can access to his email messages without having his Exchange account.  Thank you very much in advance.
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Valentina PerezExchange ServersCommented:

You can try to open OST files with Outlook but you need to make some changes because by default Outlook is not able to open OST.

-You can configure a new Outlook profile. Check that the outlook is in offline mode. You can after check in the location, if the OST file was created...and after you can replace it with the OST file that you wish to recover.

Check this link:

timgreen7077Exchange EngineerCommented:
I would suggest looking into a third party tool for this and i will post a link for you to look into below. Even with an ost file you may not get all the mail because it depends on how much of the mail was being synced to the ost. The best route to follow would be to restore the terminated user's mailbox if the retention period for disconnected mailboxes haven't expired. By default it's normally 30 days, and once you reconnect the mailbox to a user account then export the mail to a pst file. The user account can be a test account you create just to connect the mailbox, it doesn't have to be the actual terminated user account.

Here is a link for a third party tool

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Christ HaroldSoftware EngineerCommented:
Dear Author,

There are multiple solutions are available to view some files on your system. If you are using Outlook application then import OST file in Outlook to view its content.
Read This Article For Complete Steps:

or you can try the demo version of Revove OST to PST Converter Software to view OST file for free without any difficulty.

I hope this will help you

Thanks & Regards
Christ Harold
Software Engineer
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Karl Timmermans (Outlook MVP)PrincipalCommented:
You have no option other then to use a 3rd party OST2PST conversion tool for which there are many so not going to add to the chorus of suggestions - just do a search on the phrase "ost to pst conversion" or any variation thereof and you will have no shortage of results to choose from.

Once an .ost file has become "orphaned" for any reason, it can no longer be accessed by Outlook. .ost files can only be opened by the Outlook profile/email account used to originally create the file.
Mickel JacksonCommented:
After understanding your query, I noticed that your OST file is in orphan stage. I did search on google and found a useful blog which will guide you how to access data of orphan OST file. You can go through it and may find it helpful.
Thanks & Regards,
Mickel Jackson
Sandeep KumarAssociate ConsultantCommented:
If you are looking to access OST files without Exchange Server then use Kernel OST Viewer tool which can access healthy or damaged OST file easily. But if you want to convert OST file to Outlook PST then you can use Kernel for OST to PST converter tool. It can convert OST to PST, EML, MSG, MBOX, PDF & DBX file format and also able to export OST data to Live Exchange and Office 365. It supports all versions including Outlook 2016 and Windows 10 OS. Visit to check salient features of OST to PST tool and download the demo tool.
Sara TeasdaleCommented:
Generally, an .ost  file is a copy of information saved on your mail server. If you encounter problems with an offline Outlook Data File (.ost), the file can be deleted and recreated by downloading a copy of your items again. For instructions about how to recreate an ost file, hopefully the instructions in the link below can be helpful:

Recreate an offline Outlook Data File (

If recreating an OST file cannot help, I'm afraid a third-party convertor tool would be the only choice.
Without Exchange Server, you can't access OST files But if you moved all OST files in your system. then you have to need third party tool for converting OST to PST like seemit ost to pst, aryson ost to pst, Mailsdaddy ost to pst. there are several tool are available, you can pick any one of them & get healthy PST file easily. you can also convert OST to PST, EML, MSG,  file format.
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