Using OneDrive or Cloud Storage for PST Files

Last reviewed on September 21, 2014   —  14 comments

With the release of Office 2013 and it's emphasis on OneDrive storage, I've had several people ask about moving their pst file to OneDrive, DropBox and similar services.

The answer: It won't work. Outlook puts a lock on the pst file when the pst file is open. OneDrive (and other cloud solutions) continually syncs the local folder. It won't be able to sync the pst because Outlook has a lock on it and as a result, the pst file could become corrupted and data loss occur.

While you could use OneDrive or another cloud service 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 shut the computer down before its completely uploaded then try to open it from another computer, the pst may be corrupt.

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.

When you use a backup service I highly recommend verifying the backup several days after setting it up, so your sure it's getting the pst files and also every few months to insure it's still working as expected.

About Diane Poremsky

Diane Poremsky
A Microsoft Outlook Most Valuable Professional (MVP) since 1999, Diane is the author of several books, including Outlook 2013 Absolute Beginners Book. She also created video training CDs and online training classes for Microsoft Outlook. You can find her helping people online in Outlook Forums as well as in the Microsoft Answers and TechNet forums.

Please post long or more complicated questions at Outlook forums by

14 responses to “Using OneDrive or Cloud Storage for PST Files”

  1. Jim Wagner

    I found this website that someone is using his skydrive for his pst. I am skeptical.

    1. Diane Poremsky

      You should be skeptical. It won't work. SkyDrive will not sync the pst file while it is open in outlook, only one outlook can be using the pst at one time, it will not sync changes (only the entire data file), and it is limited to 2 GB file size. Finally, sharing a pst file is not going to make it an Exchange server. It just makes the same copy of a pst file on two computers. You can use SkyDrive to backup a pst or copy it to another computer if you want... close outlook, copy the pst file to the skydrive folder. Copy it out of the skydrive folder before using.

      Also, his recommendation to move the pst and wait for outlook to complain is likely result in a corrupt profile in Outlook 2007 and up.

  2. Jeke


    I want to put my Outlook 2003 pst file (600MB) on SkyDrive and copy it to another computer using Outlook 2010. Problem is can I use the 2010 version and copy it back to be used in Outlook 2003 as the current pst file? In other words move back and forth between two computers with different versions.

    1. Diane Poremsky

      It will work, as long as you move (or copy) it out of SkyDrive to use it, you can't add it to your profile in the SkyDrive folder.

  3. Jeke

    Thanks for your answer, Diane. Does that also mean a 2010 pst file will work in 2003? I thought they were slightly different in that 2010 contains more info than 2003.

    1. Diane Poremsky

      They are slightly different (but still Unicode format) and yes, they will work - I have not had any problems. If you get any error messages when you try to use a pst with both versions, let me know.

  4. Joseph McKown

    I do not want to copy it to the sky drive... I want it to LIVE on the sky drive. that is where I want to access it like it was on my D drive... What would be the issue with doing that? This way I could access it on my desktop from work, or from my Surface when I am at home. I will never access it from 2 different computers at the same time...

    1. Diane Poremsky

      The pst file can become corrupted very easily. When a file is in skydrive, it tries to sync it every time there is a change and there will be constant changes but Outlook keeps a lock on it, so it can't sync until outlook is closed. If the computer crashes or is shut down too quickly after you close, the updated pst won't be upload to the server or a corrupt copy will be uploaded. Temp files will be uploaded, which can quickly eat up server space. Using (Hotmail) or Office365 (Exchange server) or even an IMAP account is a better, safer option for sharing data between computers.

  5. Ken Isaacson


    Please tell me if you see a problem with the following: I have two desktops in different locations. I won't be using them "together"-- I'll be weeks at a time at one, and then weeks at a time at the other. When I'm leaving Desktop No. 1, I want to copy the OL pst file (say, to my notebook), travel to Desktop No. 2, and copy the pst file there. When I'm ready to leave Desktop No. 2 and go back to No. 1, copy the pst file and then put it back on No. 1.

    The important thing (I think) is that when working on Desktop No. 1, no one will be using Desktop No. 2 (and vice versa), so there's no danger of changes being made to both machines. Only one machine will be used at a time.

    This should work, shouldn't it?

    Many thanks!

    1. Diane Poremsky

      It should work, yes. If you leave mail on the server, it might redownload mail though.

  6. Mike Handi

    You referred to some tools that allow an online backup of a pst to a cloud service. I can't seem to find a service like this. Would you have any recommendations?

    1. Diane Poremsky

      You can copy a pst into onedrive, google drive dropbox etc, but you can't open the pst file in outlook while its in the cloud drive. Well, you can, but you risk corruption. If you want to backup files automatically, Mozy and Carbonite are two that can backup outlook files. There are more.

  7. Joel Bancroft-Connors

    I find it mind boggling that the company that owns and understands best how the PST operates is unable to support its use in a modern Cloud environment. It almost defeats the purpose of Office 365 when one of the most important parts can't be cloud enabled.
    There isn't even a way to sync this with

    1. Diane Poremsky

      The issue is that the pst file was never designed to work over a network - outlook keeps a lock on it. When Outlook was designed nearly 20 years ago, this wasn't an issue. The problem now is that most cloud services can't sync it and even if they could, syncing a multigigabyte file can take forever. Mozy, Carbonite, and a few others that do incremental backups do a better job, although there is always the chance that the pst will be corrupted.

      The solution is to use Exchange mailbox (best) or for email if you need to access your mail, calendar, and contacts from multiple computers instead of a pst file and POP3.

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