Outlook Oversized OST File Problem

Maximum .OST file size in Unicode is 20GB for Outlook 2007 and 50GB for Outlook 2010/2013/2016. By default the maximum size is set to 20GB. When the .OST file reaches or exceeds this limit, you will encounter one or more of the following errors:

Cannot open or load the OST file at all.
Cannot add any new data to the OST file.
Cannot synchronize the OST file with the Exchange server.
Various error messages during the synchronization process.

Adding shared mailbox in online mode

Registry Fix:
To proceed follow the steps below:

Open Registry: Start > in Search field type in “regedit” without quotes.
Navigate to HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.0\Outlook\PST for Outlook 2007, HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\Outlook\PST for Outlook 2010, or HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\Outlook\PST for Outlook 2013.
Right-click on MaxLargeFileSize in the right pane > Modify > type in value in MB in Value Data box > Ok.
Right-click on WarnLargeFileSize in the right pane > Modify > type in value in MB in Value Data box > Ok.

Archives Above 20GB will start impacting performance.

Author Details
Contributer and Author Enterprise Communications Engineer Hi Epic

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