Last reviewed on July 24, 2015   —  23 Comments

outlookiconOftentimes, Microsoft Outlook users who are leaving their current employer want to take their mail, calendar, or contacts with them and do one of two things – delete the Microsoft Exchange account from their profile without realizing the Contacts are stored in the Exchange account or they take the OST file with them, not realizing it can only be opened using the account that created it.

If you no longer have access to the computer that was used to create the OST or you don’t have a restore point, you’ll need to use a tool to recover the contents of the OST. A list of these tools is below. Note that OST2PST is free but will only work with OST files created by Outlook 2002 and older. If you aren’t sure what version of Outlook you used, try it; an error means the OST is not the correct type.

If your company uses a group policy that blocks PST creation, your choices are limited to exporting calendar and contacts to CSV (or Excel, if you have Excel at home). If you don’t have many calendar or contacts, you can forward them to a personal address. If using Outlook 2007 or 2010, you can send your entire calendar as an iCal.

Note: Check company policies before taking home the contents of your mailbox.

Restore Exchange Account

If you deleted the Exchange account, you may be able to recover the account if your operating system supports system restore and you only recently deleted the account. If too much time has passed you are less likely to have a restore point available.

  1. Open the system restore application. In Vista it is at Start Menu, Programs, Accessories, System Tools.
    Or enter %systemroot%\system32\rstrui.exe in Start search field or Start menu, Run.
  2. Pick a date just before the profile was deleted.

When Windows restarts the account will be back and you can move or export the contents of the OST to a PST. Then either delete the account or run restore again to return to the point made before the restore.

Method 1: Archive

You can use Archive to move or copy many items to a PST – this method is best when you want to move almost everything in your mailbox. Note that you cannot archive Contacts. Set the AutoArchive default in Tools, Options, Other, AutoArchive and apply it to all folders. Then go to File, Archive and run it.

AutoArchiving uses the last modified date so you’ll need to use a low number when archiving recent items. If you use Outlook 2007 or Outlook 2010 you can force AutoArchive to use the Received Date. See Using Microsoft Outlook’s Autoarchive feature

If you use this method and also need the Contacts, you’ll need to move them to the new data file.

Method 2: Export to a PST

Although Export is not usually recommended, when converting an OST to a PST, Export is generally a quick and easy way to move all content from the OST to a PST or ven just the calendar and contacts. If your company blocks the creation of PST files, export to CSV or Excel format.

Method 3: Move the items to a new PST

Create a new PST in your profile and drag the folders you want to take with you to the PST. This method will preserve custom views and forms published to folder.

Dragging default folders, such as Inbox, Calendar, and Contacts, brings up a message that you can’t move default folders. The contents will be copied instead, with the folder named Inbox (1), Calendar (1), etc.

Method 4: Forward by E-mail

If you don’t have too many items you want to keep, you can email them to your personal email address. Select the item(s), right click and choose Forward. If you have many, you could drag them to a folder in My Documents, then zip the folder and email the zip file.

Outlook 2007 or Outlook 2010 users can email the entire calendar as a single iCal, provided they use Outlook 2007 or another calendaring application that supports multi-event icals at home. Older versions of Outlook do not support multi-event icals.


Tools in the Spotlight

DataNumen Exchange Recovery

DataNumen Exchange Recovery repairs and recovers corrupted Microsoft Exchange offline storage (.ost) files. Exchange Recovery can scan orphaned OST files and recover mail messages and other items, including folders, posts, appointments, meeting requests, contacts, distribution lists, tasks, journals and notes. The recovered items are saved in PST format readable by Outlook, Other important features: recover attachments and deleted items, recover oversized 2GB OST files, support to convert OST files into PST files.

Kernel for OST to PST

Kernel for OST to PST is an advanced solution to deal with OST files that have become inaccessible or unusable due to Exchange server corruption or user account deletion. It effectively repairs OST file and saves its email data to PST format to make it easily accessible and usable with MS Outlook. Individual email items along with their attachments can be saved to PST, DBX, EML, or MSG format. It supports all versions of MS Outlook and MS Exchange for repair and conversion. Free trial version of OST to PST tool is also available.

Recoveryfix for OST to PST

Exchange OST to PST email conversion tool to convert OST file to PST file. Convert working or unusable OST file to into PST file. Use it to migrates all Outlook items from Exchange Offline Storage (.OST) file to Personal Storage File (.PST). Software converts and repairs the offline storage file (ost) to personal storage (pst) file so that it can be easily accessed with Outlook. Other saving options include .EML and .MSG where former is accessible with Outlook Express and latter with Outlook. If the ost file gets corrupt or damaged, OST to PST functions as ost recovery software.

Stellar OST to PST converter

Stellar OST recovery software is the most efficient tool to convert Outlook OST file to PST file. The software successfully recovers all the components of .ost file such as emails, contacts calendar entries, attachments etc. The tool is able to convert OST file to working PST file in any instance of corruption. Free demo version is also available that previews all recoverable items of inaccessible .ost file.

Tools - Convert OST to PST service

This is an alternative way to convert OST file to PST. If you don't want to buy specialized software you should use service. You don't need any special knowledge. Just send the order for converting. You'll receive detailed instruction and after 8-24 hours you'll receive PST file which can be opened by Outlook. All types of data from OST (emails with attachments, calendar, contacts, tasks, notes) will be available in PST file.

Kernel OST Viewer

Kernel OST Viewer is a FREE utility to view the contents of OST files. It does not require Outlook installation. A connection with Exchange is also not required. Just select the OST file and it will mount it in its Outlook like GUI instantly.


Free OST to PST Converter. Convert OST to PST, even if files are inaccessible. Using Enterprise Edition convert OST files which are linked or unlinked to Microsoft Outlook. Use OST2 to transfer data from Exchange to Microsoft Outlook, make your Exchange account emails, calendar, contacts and other items accessible through Outlook. To prevent Offline Storage .ost file's data loss, back up data as a PST file. Supports 2013 and older OST files.


Free tool to convert older *.OST files to *.PST files. Works with ANSI format only, will not work with OST created by Outlook 2003/2007.

PST Merger

Merge PST files with free software for Microsoft Outlook that combines PST files into a single PST file. Merge selected folders from PST files, such as, Inboxes, Calendars, Contacts, Journals, Tasks etc. to another PST file. All your data stored in original PST files will be preserved and merged without making any changes to the original files. For more flexible PST merging options use PST Merger Pro Edition. Merge, move or copy specified Microsoft Outlook folders from unlimited PST files at once. Move or copy specified Outlook data from one PST file to a selected PST file without the need to merge all content from both PST files.


  1. Floyd Shiffman says

    Hi Diane, I saw a post below that you responded to to help someone who deleted a exchange acct. and I made the mistake of deleting two of my non active email accounts on my Iphone which then deleted them off my laptop with all my contacts. I tried the system restore but it didn't bring anything back on those email accts? Can you please help me out?

    What type of account did you delete? If exchange server, see

    How long ago did you remove the account? If recent, you can use system restore to get it back.

    Diane Poremsky [MVP - Outlook]
    Outlook Daily Tips | Outlook & Exchange Solutions Center
    Subscribe to Exchange Messaging Outlook weekly newsletter

    • Diane Poremsky says

      Deleting accounts from an iphone should not delete them from the laptop. Deleting the contacts from *within* an account on the iPhone will delete them from Outlook or your mailbox. Check the Deleted items folder and recover deleted items command to see if you can find them, if not, you will need to have your mailbox restored. System restore won't work because the iphone deleted them from the Exchange server- the only way to recover them if they are not in deleted items or deleted items recovery is by recovering the mailbox from backup. Sorry.

      Now, if you happened to have a second profile set up with this account that has not been used since you deleted from iphone, disconnect that computer from the network (so outlook can't sync) and open Outlook to the profile then export the contacts. Go online and import them.

  2. Garrett says

    Thanks for this list, Diane. It's a great cross-section of tools for viewing ost files and for the benefit of IT support or sys admin's to maintain and service their users' accounts. However, I'm a new hire with legacy data trapped in an ost from a previous employer. It is all I could export from there before leaving and therefore without a translation into an actual pst file it's practically useless. Without the ability to use the attachments and extract email addresses, contacts, etc., it's more of an inconvenience than productive. Is there a software product that will allow me to not just view the ost but actually translate it into a pst file that I can add as an Outlook data file? I understand that developers want and deserve to make money from their efforts. But spending $50-$200 to carry my legacy email into my new job once just isn't worth it for me. Do you know of a program that would allow me to get a pst file just once? Thanks,

    • Diane Poremsky says

      Did you try OST2 PST Converter for Outlook? That is supposed to be free. Otherwise, if you have a Unicode ost, you'll need to pay to have it converted to a pst if you need to convert it.

  3. Brian Diana says

    HI Diane I have noted more and more of the office 2013 email addresses are being setup at ots even if they not exchange addresses

    • Diane Poremsky says

      Yes, any account type they syncs to the server now uses an ost file. That would be IMAP and (Hotmail), with only POP3 and user-created date files using pst.

      IMHO the only problem with this is with IMAP - if the user decides to keep calendar and contacts in the IMAP ost, they need to export the 'this computer only' folders to make backups, not the entire data file.

  4. Wes T says

    The computer used by our senior project manager locked up and was then powered down hard. When the user rebooted and returned to Outlook 2010, all mailbox contents were gone. On the exchange server 2003 System Manager this user's mailbox still contained the same amount of data as it had pre-crash, but we could not gain access to it in Outlook or OWA- somehow it was corrupted during the power down. After Googling this problem I ended up reading your article. I decided to purchase the Stellar Phoenix software which was less than $200. The online purchase and license delivery for Stellar Phoenix seemed rudimentary and made me a bit nervous that I was about to be scammed, however, the end result was perfect. I extracted the .OST file from my user's local hard drive and allowed Stellar Phoenix to chew away at it overnight. The output was a large .PST file containing ALL of the user's lost mailbox contents. The PST opened perfectly in Outlook 2010 and even the structure of inbox sub folders rendered correctly. What a huge relief! As this user was mid-project on several multi-million dollar stadium assignments, this was $200 I was glad to spend! Now if only there was a way to purge the old "corrupted" data which is still lurking somewhere in the user's exchange mailbox... Thanks for the helpful article!

    • Diane PoremskyDiane Poremsky says

      Sorry, I'm not aware of any because Mac clients don't use ost files (and don't use pst, but they can import pst files).

  5. Karry G. says

    Dear Diane. As per your software suggestion I tried stellar ost pst converter for Outlook file conversion. Of-course it worked fine, but can you recommend any free ost to pst converter too!

    Looking for your response!

    Karry G.,

  6. Karry G. says

    No problem Diane! I've done ost pst conversion with Stellar tool. BTW, you're doing such a fantastic job through your blog.

    And, thanks again for your valuable fast response!

    Karry G.,

  7. Glen Wenzel says

    Hi Diane, I am thinking of using the OST2 program to convert a large OST file into a PST. However, the OST file is 6.7 GB in size. Is there not a limit of roughly 2 GB on the size of a PST file, after which Microsoft says it cannot guarantee the PST file's stability ? (The OST file is from Outlook 2010.)

    Also, am I correct in thinking that the converted PST file would be roughly the same size as the OST file ?

    Thanks for a great article. It is VERY helpful !!

    Glen W.

    • Diane PoremskyDiane Poremsky says

      The (new as of outlook 2003) Unicode pst format is unlimited so it should work fine.

      As for pst/ost size comparisons - it's really difficult to know but it will likely be close to the same size. The converted pst might be as much as 25% larger (messages in pst file can be larger because of the way Exchange stores messages) - it might be a smaller if there is a lot of "white space" that wasn't compacted. Because outlook doesn't compact until there is 20% white space and the computer is idle, there is a theoretical 1.20+GB of white space in the ost. The larger messages in a pst and white space in the ost can cancel each other out.

  8. Glen Wenzel says

    Hi Diane, Thank you so much for your quick reply and the valuable information about the PST data files and their sizes. Knowing that the 2 GB limit is no longer a concern, is extremely useful and means I will not have to keep monitoring them as I've been doing up till now. Plus, I know now that creating a backup copy of the OST file will not be a problem due to its large size.

    Please know how much your expert assistance is appreciated. Thanks again.

    Glen W.

  9. John says

    Use Mailstore Home (free for personal use!). If you have your emails via Exchange then just select Microsoft Outlook from the menu. You can also configure access to email server via manual settings.

  10. Theodore Weitz says

    Hi Diane --

    This is a very helpful site. I recently had my computer in for repair and when they did a system refresh, it preserved my document file, but a large critical file is now shown as an .ost when I search in the "windows.old" files that were created. Since I did not have an exchange server, I can't figure out why this happened, but I need to recover the valuable information it contained. I am using the Microsoft office 2013 software, and was wondering if the tools you described will all work with Office 2013. I know that previous versions monkeyed enough with the fle structure that what works with one does not necessarily work with the next version.

    • Diane PoremskyDiane Poremsky says

      I'm guessing it was an imap data file - the messages in it should be on the server but if you had contacts and appointments in the 'this computer only' folders, they would be in the ost. The last time I tried, the recovery tools did not work with the imap ost files, but it's worth trying (because restoring the old windows is a pita) You could try using a pst repair tool too.

  11. Brit says

    Buyers Beware:
    I archived my whole company to PST using this tool, and had it imported into a 3rd party online archive. After doing this, users would find no results using To or From -- but doing a basic text search of the address would find results.

    I investigated this an determined that the Stellar EDB to PST does not actually keep the original format intact in the PST, despite this info on their web page:

    "Converts MS Exchange database files (EDB) into corresponding PST files and extracts all your mail components with their original format absolutely intact"

    The issue is that this converter does NOT bring over the true header information (what is seen if you crack open the email and look at the source). This is a problem for indexing systems that rely on the actual data and not what is displayed in the From/To/Subject part of an email.

    You can verify this by looking at the properties an email from your inbox, then look at the same properties of the same email after extracting it using Stellar.

    I requested a refund as I will have to purchase another OST to PST tool (Lepitde OST to PST Converter), which does the job correctly and DOES carry over all of the original forma absolutely intact, but was denied.

    So if you are using this in an enterprise environment and need that information, Stellar will not provide that. Otherwise the product is fine, but for me, it makes it useless.

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