Resolve Outlook OST File Exceeded Its Default Maximum Size Issue

admin | September 15th, 2017 | MS Outlook

OST files are a part of MS Outlook consisting of a replica of data stored on an Exchange server. It’s store all user’s mailbox data like emails, calendars, contacts in offline mode. This enables a user to work even when there is no internet connectivity or some exchange server issues. But like Outlook PST file, OST file also experiences various problems. One of them is “Exceeded it’s default maximum file size” while sending or receiving emails.
This blog will focus on various causes and solutions for oversized and Exceeded default OST file size problem.

Reasons for OST File Exceeded its Default Maximum File Size are:

  1. The error might occur when your OST/PST file got corrupted due to any reason.
  2. OST file becomes inaccessible due to exchange server connectivity or synchronization issue.
  3. When your Outlook data file has more content than the specified size limit.

The default maximum file size (OST/PST) limitation in various Outlook Versions is:

  • Outlook 2002 and earlier versions : 2 GB
  • Outlook 2003 and 2007 : 20 GB
  • Outlook 2010 and above : 50 GB

Solutions for OST File Exceeded it’s Default Maximum File Size

  1. Sometimes deleting the content from OST file can resolve the exceeded file size problem but that is not a permanent solution as the data you deleted is proportional to the file size. Therefore to reduce the size of OST file you can either use Synchronization Filter method or you can compact the size of OST file on advanced tab settings of exchange account. Synchronization filter Method restricts particular data items to be synchronized from Exchange mailbox to OST thereby reducing the size of OST file to some extent.
    Steps to be followed for Synchronization filter method:

    • Right click folder and click the Properties Button
    • Click on Synchronization tab and then Select Filter Option
    • Now provide the appropriate criteria for filtering the data items needed to be stored in the folder.
    • Click OK Button and Re-Open MS Outlook

  3. After performing Synchronization filter method you can further reduce OST file size using compact now option. MS Outlook does not reduce the size of OST file when you delete the data item from it instead it shrink the OST file. This shrinking of file is done according to a particular threshold. You can manually perform the compress procedure instead of waiting the file size to be reached at the specified threshold.

    You can use “Compact Now” option to perform the same. Steps to be followed for Compact Now method are:

    • Open Control Panel and click on Mail
    • Then select data file in Mail setup wizard
    • Select the OST file that you want to shrink and click on Settings.
    • Microsoft Exchange setting wizard will open. Then select Advanced tab option followed by Outlook data file setting.
    • Browse and Locate the OST file thereafter click Compact Now.


“OST file exceeded its default maximum file size” is the most common problem faced by Outlook users. Any of the above manual method can be used to resolve the problem. While compressing the file size, data integrity is also maintained.