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Outlook: Max Message Store Errors

Outlook 2016

Outlook 2016
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Microsoft Outlook: Dealing with Maximum Message Store errors

Upon occassion, I run into errors with some of my clients with regards to their Microsoft Outlook message store. The Outlook message store is a size limit on how big your .pst or .ost file can get in Microsoft. Once it hits that limit, you will receive errors and be unable to retrieve new mail.

Fortunately, though, the limit of the message store is pretty big, so it isn’t a common issue. Here’s a list of the message store defaults for various versions of Outlook:

Outlook 2003 and 2007

Outlook 2010 and later

20 GB


The good news is that if you have a client that is pushing the envelope with regards to the size of their message store, you can increase these levels using the Windows Registry Editor.

Windows Registry Editor

  • Search for regedit.msc; this is the application that loads the Registry Editor.
  • Go to HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\xx.0\Outlook\PST (the xx will be a numerical representation depending on the version of Outlook you are running. For Outlook 2016, it will be 16.0)
  • Look for MaxFileSize and WarnMaxFileSize in registry entries. If you don’t see them, make new D-Word entries and name them the names listed. No spaces, make sure capitalization is correct.
  • Once you make them, double-click on the MaxFileSize to open up the window to modify it. Click on Decimal, and type 102400 (to set the message store to 100GB). Then click OK
  • For WarnMaxFileSize, do the same thing but set it to something like 90000, then click OK.

Once you have done these things, close out Registry Editor and load up Outlook to see if it takes care of it for you.

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