Hi @Niraj Shah ,
Based on your description, are you referring to the size limit of the data files in the Outlook client?
Did you encounter any specific error message?
If you meant the size limit of Outlook data files, as far as I know, in Outlook 2010, 2013, 2016, 2019 and Microsoft 365, this limit is set to 50GB.
Based on my search, you can increase the limit via the registry to manage the Outlook data files size.
Important: Follow the following steps carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.
To modify the registry, here is an document for reference: https://www.msoutlook.info/question/large-exchange-mailboxes-and-the-ost-file-size-limit
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
Step 1: Press ‘Windows’ and ‘R’ keys together to open the Run dialog box
Step 2: In the Run dialog box, type registry and press Enter
Expand the registry key due to your Outlook version:
Step 3: Create the following 2 new DWORD values.
In addition, I also found a document which introduces several ways to clean up items in the mailbox and how to manually compact the OST file after deleting items.
If you have an Exchange or IMAP account, it is recommended to modify the offline settings to reduce the offline emails.
File> Account Settings> Account Settings>select your account>Change> move the Sync Slider below: mail to keep offline.
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