Last reviewed on July 2, 2015   —  34 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 in most services and is not recommended in any service. 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.

DropBox does incremental backups (reducing the need to upload a large pst in full each time), however, you need to make sure you close Outlook and wait for all updates to be uploaded before shutting down the computer, otherwise accessing the pst from another computer could result in lost data or a corrupt message store. Always keep a backup copy of the pst. This is an unsupported scenario and Microsoft will not provide support for it.

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.


    • Diane Poremsky says

      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.

  1. Jeke says


    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.

    • Diane Poremsky says

      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.

  2. Jeke says

    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.

    • Diane Poremsky says

      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.

  3. Joseph McKown says

    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...

    • Diane Poremsky says

      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.

  4. Ken Isaacson says


    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!

  5. Mike Handi says

    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?

    • Diane Poremsky says

      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.

  6. Joel Bancroft-Connors says

    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

    • Diane Poremsky says

      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.

  7. Philip Cartledge says

    First of all let me come clean upfront because I do NOT run my .pst file from the cloud. But please bear with me and read on, because what I do works.

    At Location One my home network consists of two desktop PCs both running Outlook 2013. At Location TWO I have one desktop PC running Outlook 2013. In addition I have a laptop PC which also runs Outlook 2013.

    I run dropbox on each of the four computers and my .pst file is stored in D:\dropbox. I can't remember how long I've been using dropbox, but since I'm an enthusiastic 'fools rush in' sort of early adopter, it must be for some years now. Dropbox is able to upload the incremental changes that I've made to the .pst to the cloud. I am, however, careful never to have 2 instances running at the same time, and I'm careful never to shut down the PC before dropbox has finished uploading (not long anyway). My .pst is currently a pretty tidy 326,127 KB. This system works a treat for me and in the years that I've been using dropbox I've never got into a tangle and never had a corruption issue.

    More recently I've tried but unless I've misremembered, nested folders are not possible & it just doesn't cut the mustard anyway compared with the real thing.

    A few years ago, I gave in to the MS hype and decided to try OneDrive instead of dropbox. That was no good at all because OneDrive insisted on uploading and then downloading the entire .pst. It was only at that point that I realised how clever dropbox was. Fibre and cable connections are not available to me and so the experiment was very brief indeed. I might add that OneDrive also lacked LAN sync which is so useful for me when I'm at Location One.

    So, Ken Isaacson, try it out and I think you'll soon forget about USB sticks.

    • Diane PoremskyDiane Poremsky says

      Dropbox is definitely better than OneDrive and with your smallish pst file, it is less of a problem... but I'd still keep a backup copy, just in case....

  8. Roberto Estrada says

    Dear Ms. Diane: Good day. I want to move away from PST files. My company has given me a large amount of storage space in my cloud inbox in Outlook - we just migrated to office 365; I am going to create folders and move the contents of the PST files to the inbox. I know the cloud service will back up but for peace of mind: can I back up those folders to my PC?

    • Diane PoremskyDiane Poremsky says

      You could make regular exports to a local pst to have as a backup, but it's really not necessary. Accidentally Deleted items can be recovered for at least 2 months after the deleted items folder is emptied.

  9. Greg says

    Hi Diane, I currently work through an exchange server based email. I am trying to find out how to link my email to my onedrive account so that all emails are stored on the cloud. I currently work on the basis as mentioned above where I have a .pst folder set up which runs on google drive. I know now that this isn't the best option due to the google drive syncing the whole file on a daily basis (currently sitting at 15Gb and getting bigger). From what I have read it is possible to link up your exchange email to onedrive through office 365. Am I correct and if so can you point me in the right direction in getting this set up?

    • Diane PoremskyDiane Poremsky says

      No, you can't link Exchange mail to onedrive. You could save it as msg files to the OneDrive folders, but that is not recommended. The only option (and its not a good one) is to have connect to the Exchange mailbox - it'll access the mailbox using POP3.

      Is your exchange email not available from the internet?

  10. George says

    My pst file is around 10G and it's stored on a second HD in my pc which makes it really really slow to access. I dont want to go to an SSD solution at the moment, however since i got much space on the cloud (via OneDrive that comes with 365 + Dropbox) can i take advantage of that space in order to make access faster??

    • Diane PoremskyDiane Poremsky says

      No, you can't move the pst to OneDrive. If you have room on the main drive, you can move the pst to it. That might make it faster.

  11. Mike Worley says

    I'm considering going to Office 365 but have concerns about this issue. As I understand from the Microsoft tech support people, I can move the contents of my pst file to an ost file on the exchange server (one drive?) and then in that way access my mail, contacts, and calendar from multiple computers. Is that correct? My plan is to have 365 on my home PC and on my macbook, and the outlook app on my iPhone and iPad.

    • Diane PoremskyDiane Poremsky says

      Arte you considering Office 365 Business with an Exchange mailbox or just the Office 2013 software (in the Home subscription)?

      Exchange server does not use OneDrive to store email, (formerly Hotmail) does not use OneDrive to store email. At this time, mac won't sync with calendar and contacts. The apps on the devices will sync with either Exchange or

      You can import a pst into an Exchange mailbox; to move mail into, you need to set the account up as an IMAP account to move the mail over. Calendar and contacts need to be exported then import at and will sync down to Outlook.

  12. Flaviu says

    I am using Dropbox for more than 2 years with PSTs archive in total of more than 60 GB. How this works is that when outlook is running the sync doesn't work, but when you close the Outlook, Dropbox is doing a change check, and if nothing happens nothing is uploaded, if there are changes, it automatically upload just the differences, even the files are very large, like 5 GB. I have never had any files corrupted, and I want to mention that I am a very heavy email user.

    • Diane PoremskyDiane Poremsky says

      You are really lucky. It is very risky, especially if you are opening the pst files with multiple versions of Outlook, and is not supported.

  13. Meg says

    Can I use google drive as a backup for outlook 2010. It is syncing right now. To restore couldn't I just download the whole pst file from google to somewhere on my c drive & import from outlook? In that process are you saying that I will import a corrupted file? What is the best way to backup outlook?

    • Diane PoremskyDiane Poremsky says

      As long as it's a copy and outlook isn't using the pst, yes, it can be stored in google drive.

      The best backup is to make a copy of the pst.

  14. Meg says

    Ok after rereading your first sentence above, what if I only back up 1 time a week & close my google drive until I want to back up. When I back up my pst files I'll make sure outlook is closed? Would they still be corrupted?

    • Diane PoremskyDiane Poremsky says

      As long as it's not to big for google drive, you can keep a copy in it (or any other cloud service). The problem arises when you move a pst there and open it in outlook.

  15. Philip Cartledge says

    Please see my Reply posted 22nd Jan 2015 for more information, but it seems that my message has not yet got through.

    My .pst file (now 406,409 KB) RUNS very successfully from my Dropbox folder on my various devices, and has done for several years. I've NEVER had a problem PROVIDED I make sure that it has updated itself if I'm switching devices (I have 4 devices in my main home). If I hover my mouse over the Dropbox icon in the taskbar, it helpfully tells me "outlook.pst is downloading". Of course I avoid using Outlook on more than the one device here at home. The main use of Dropbox is when I'm at my London flat.

    I've no idea about Google Drive, but Dropbox is fantastic because it identifies incremental changes made in the .pst and ONLY makes those changes. Therefore updating is achieved very quickly. Unless OneDrive has recently become more sophisticated, it uploaded and downloaded the entire file each time. In addition Dropbox also enables LAN sync which OneDrive didn't when I experimented with it.

    Perhaps someone would be able to tell me whether Google Drive and OneDrive now allow:

    1. LAN sync
    2. Make only incremental changes

    Life would be so much easier if I allowed myself to 'give in' to MS and used OneDrive instead of Dropbox, but until OneDrive is able to do the above, I am forced to stick with Dropbox.

    Many thanks

    Philip Cartledge
    (High Peak, UK)

    • Diane PoremskyDiane Poremsky says

      It's great that Dropbox now does incremental backup (they didn't when the article was originally written) but it is still risky and you should keep a backup copy of the pst. Just forgetting to close outlook and leaving a computer on before opening outlook on another computer can corrupt it as can shutting outlook and windows down before changes sync up then opening it on another computer.

      If something goes wrong, Microsoft won't help - they do not support using cloud services for pst storage.

      AFAIK, no, neither onedrive or google drive support LAN sync or incremental changes.

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