Increase Maximum Size of PST and OST for Microsoft Outlook by Registry Entries

article #1073, updated 66 days ago

For a very long time, it was thought gospel that Outlook had hard caps on size of PST and OST files, which equals a hard cap on the size of a mailbox that Outlook can see. This has, apparently, changed. 100-gigabyte OSTs are possible, and larger. It is thought that very fast hard drives primarily, and certainly also good CPU and lots of RAM, are needed to reliably handle huge mailboxes and PSTs without corruption. Here is a method by registry entries. It’s also possible by Group Policy.

https://support.microsoft.com/en-us/help/832925/how-to-configure-the-size-limit-for-both—pst-and—ost-files-in-outloo

https://www.msoutlook.info/question/increase-pst-file-size-limit

Today it was found that an Office 2019 installation via 365, did not have any of the registry keys involved. After creating them manually in Regedit, the desired results did occur. These very registry entries are also created by the Group Policy method.

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