Outlook 2010 OST file issue RRS feed

  • Question

  • Hello everybody, 
    I work as a system admin. A few users in my account have been facing a weird issue for the past week and I hope you guys can help me out with this. Thanks in advance. 

    We are using Outlook 2010 as email client with an exchange server in place. Management and configuration of the exchange server is done by our client IS team. One particular team with in my account facing an issue with their outlook for the past one week. The issue is their Outlook profile size (Outlook data file) keeps growing and have consumed almost 3/4 of their hard disk space. Since it is a virtual environment we keep adding the additional hard disk space whenever these users running out of space and whatever space being added is consumed by the profile within a short span of time (say one day, for an example 5 GB space consumed within two days). Interesting part is that these profiles are configured to archive the emails and the archive files are placed in a common network share drive. The mail box size for these profiles are reflecting between 60 MB to 460 MB 
    * How the size of the data file keeps increasing though the users archive their emails and also delete unwanted emails regularly (Even the deleted items folder is also empty)? 

    * How can the size of the outlook data file grows to GB's with the size of their email box is only in MB's? 

    Can someone please help me to resolve this issue?
    Thursday, May 5, 2016 7:50 AM


  • Hi,

    In the .ost files, sometimes there is some white space that also consumes the storage, I suggest you check if this helps reduce the .ost size:

    In Outlook, click File -> Info -> Account Settings -> Account Settings -> Data Files -> Double click on the .ost file -> Advanced tab -> Outlook Data File Settings -> Click on the Compact Now button. Then check the .ost file size again.

    You mentioned the actual mailbox size is between 60 MB and 460 MB, but the .ost size is way bigger, so I suggest you check these two options below:

    In Outlook, click File -> Info -> Account Settings -> Account Settings -> Data Files -> Double click on the .ost file -> Advanced tab.

    Have you checked "Download shared folders"/"Download Public Folder Favorites"? If yes, these may also consume some storage in the .ost file, please uncheck them and click OK, compact the .ost file again to check the result.

    By the way, before the issue is resolved, a workaround could be switching to Online Mode instead of the Cached Exchange Mode, then Outlook won't use the .ost file as the local mailbox cache.


    Melon Chen
    TechNet Community Support

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    Friday, May 6, 2016 5:27 AM