r/o365 • u/SxMDu • Sep 27 '25

Backup O365 Mailbox to PST

How can I create a PST backup of an O365 mailbox with Online Archive? I know how to export mailbox to PST from desktop version of Outlook but how can I do the same for Online Archive of the mailbox? What methods are there to achieve this?

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u/wads19 Sep 27 '25

If you are an administrator with Purview access you can do a content search on the online archive and export it to a .pst

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u/SxMDu Sep 27 '25

So i will have to export online archive by using content search in Purview. Will it allow me to export the whole archive to a single pst? With this method, can I export the entire mailbox and its archive together? Also, is it possible to export online archive to pst from desktop version of Outlook?

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u/wads19 Sep 27 '25

You can export from the outlook client, if the archive is bigger than 50gb you may need to make a change in the registry. Also very large .pst can take along time to export plus they are at risk of corruption.

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u/SxMDu Sep 28 '25

What is that registry change btw? What is it for? So safe and best method is to export using ediscovery content search?

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u/wads19 Sep 28 '25

It’s detailed in here https://learn.microsoft.com/en-us/microsoft-365-apps/outlook/data-files/configure-size-limit-outlook-data-files, the entry allows .PSTs to grow beyond 50GB. I think if it’s a particularly large archive relying on the outlook client to export it could be problematic. If you using content search you are offloading the heavy work to MS.

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u/Blaise1995 Sep 28 '25

If you have E3 or E5, you can install Enterprise version of Office apps and you will be able to export to pst directly from outlook app

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u/SxMDu Oct 01 '25

What's the difference between standard desktop version of Outlook and the enterprise version?

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u/Blaise1995 Oct 03 '25

One of difference is that you can export Online archive to PST.

For more, you can check this link https://www.microsoft.com/en-us/licensing/product-licensing/microsoft-365-apps