Tip 1013: Can you use OneDrive, DropBox or other cloud storage for pst files?

I've had several people ask about moving their pst file to OneDrive and similar cloud-based services.

Sorry, no can do. It won't work and could result in a corrupt data file.

Outlook puts a lock on the pst file when the pst file is open. OneDrive continually syncs the local folder. It won't be able to sync correctly when Outlook is open because Outlook has a lock on the data file.

While you could use cloud storage to store backup copies of your data files, its not recommended due to the large size of many pst files: uploading a large data file can take "forever". If you want your Outlook data in the cloud, use Office 365 or other hosted Exchange service, Hotmail/Outlook.com or an IMAP account. Office 365/Exchange will store all Outlook data online, while Outlook.com/Hotmail is email, calendar, and contacts only.

Note that Hotmail Tasks will sync only with Outlook 2013 when you use EAS. The Outlook Connector does not sync tasks. IMAP is email-only.

There are online backup services that can backup pst files when Outlook is open and incrementally backup the pst, so only changes are saved. These are safe to use because they are designed to work with Outlook data files. However, unlike backing up a file to OneDrive or DropBox, you can't download the pst file to another computer or when needed. You need to restore it using the backup application.

Update 1/2012: I tested SugarSync to sync the folder where the pst were stored. It won't sync the pst files, but is syncing the temp files Outlook creates. When I received notification that I was almost out of space, I used the SugarSync File Manager to clean out files I didn't need and empty the Deleted Files cache. It turns out that I had several GB of deleted files going back months. I permanently deleted the pst.tmp files to reclaim 2 GB.

SugarSync deleted items folder

Published August 9, 2012. Last reviewed on September 15, 2014.

  • Carlos Ascensão

    I use my .pst file on Dropbox since July 2011.
    Every time I close Outlook it starts synchronising,
    The size of my pst file is over 13 GB.


  • Bruno Verschraegen

    Great info! Any chance you can list a few online backup solutions that can deal with open outlook file and incremental backups (we are based in Europe, Italy)?

  • Trevor

    I use Jungle Disk (jungledisk.com) to back up my computer, including .pst files. It does back up open .pst files incrementally. But, moreover, you can subsequently download the .pst (or any other) file to the same or a different computer. The back-up drive can be viewed (in Windows Explorer or another file manager) as a virtual on-line drive, and you can simply drag & drop files across either way. (Note that this facility is available only with the so-called 'Legacy' back-up option, and not with the 'Back-up vault' option.) It will also automatically store a fixed number of previous versions of each file if you use the appropriate settings.

  • Trevor

    In response to Bruno, I'm based in the UK. I believe Jungle Disk uses Amazon & Rackspace servers with a choice of US or Europe as the location.

  • Trevor

    Diane, you state: "Tasks are included only with Outlook 2013." And Outlook 2010 surely? Or have I misunderstood your meaning?

  • Diane Poremsky

    Syncing tasks between Hotmail and Outlook is limited to Outlook 2013 using EAS. The Outlook Connector doesn't support tasks (much to the annoyance of smartphone users)

  • Trevor

    Sorry, you didn't mention syncing at all in that paragraph - i read it as just discussing what options had what features.

  • Diane Poremsky

    Yeah, I realized that when you asked about it. I'll try to make it more clear. Thanks.

  • Rich

    Without being able to use a service like Dropbox to auto-backup a .pst (or .ost) file... which is a major feature for such a service... how would you reccomed backing up data stored in a Hosted Exchange account? I currently export the data weekly to a .pst file and store that file in Dropbox. Each week I overright the previous week's file (which keeps my Dropbox size small... but still allows me access to all my historic Outlook data through Dropbox's feature of restoring all previous versions if needed).

    My question is - is there a more automated way of backing up Outlook data that is housed in a Hosted Exchange account? Maybe storing the .ost file in Dropbox (if there was a way to confidently convert a .ost to a .pst file)?

  • Diane Poremsky

    You can use the services for backup copies, but shouldn't use them for an 'in use' pst.

    An ost file can only be opened by the account/profile that created it, so storing the ost (or a copy) in dropbox won't work (well, it will work, but you'd need a recovery tool to get the contents out and they are expensive).

    For your situation, exporting to a pst file is generally the best solution. Because the pst is not opened in your profile after the export, Dropbox works fine for it.

  • Rich

    Thank you...

    I was just hoping there was some automated way of storing the information in Dropbox so I didn't have to manually do an export each week (all my other backup processes are automated and I only need to check up on them once in awhile to confirm they are functioning properly).

    Thanks again... I'll keep looking for an automated solution to backup my Hosted Exchange accounts.

  • Diane Poremsky

    You'll need to do the export each week, but you could use VBA to automate the process for you. I'll see if I can put something together. If you don't think you'll ever need to recover the data, you could copy the ost file to dropbox. Then if the time ever comes where you need to access it, you could buy the software to convert an ost to pst- it's around 100 - 150US currently. It's possible you'll never need it... and if you value your time, could 'save' the cost within a few months.

  • Rich

    Thank you for the offer to write a VBA process... but it's not necessary... I'll just do the manual export for now.

    I considered moving the .ost files to Dropbox and then using a tool in the future to convert to .pst if I needed it. My concern was (1) would Outlook let me move the .ost (if not, I didn't want to manually copy it... I might as well continue with my current export option) and (2) how well would the .ost to .pst converter work (i've never used one and I questioned how well they would work... and my Outlook data is very important to me and I didn't want to leave it to chance that it may work).

    Thanks again.

  • Diane Poremsky

    When its fairly easy and is something useful that will benefit others, I don't mind... but in looking into it, VBA can't access the export commands, so you need to walk the folders and copy each message. It's really not a good solution for more than a few folders.

    Manual export looks to be a better deal. Or, just copy the ost and hope you never need it. :)

  • Greg

    I've had multiple .pst files (different profiles) in dropbox for at least a year, with no problems. Obviously dropbox can't start synching while outlook is still open, but that's the case with all programs. The only problem I have is that I have outlook set to leave messages on the server, so if I bring up outlook on the second computer and check mail, I end up with duplicates in the inbox. I solve this by making the second computer read-only. But it is priceless to have access to both inbox and sent folders on both computers, and also obviates the need for backing up the .pst files.

  • Jamster

    Just get a Blackberry then and bb desktop it syncs everything to the smartphone.