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Outlook cached mode and OST files

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Outlook cached mode and OST files

How classic Outlook caches mailbox data locally — what an OST file is, when to use cached mode, and the modern alternatives.

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01

What cached mode does

In cached mode, Outlook:

Solving Microsoft 365 · www.solvingmicrosoft365.com/guides/outlook-cached-mode-and-ost-files

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02

Cached mode tuning

Group Policy and Intune configuration can:

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03

The new Outlook for Windows

The new Outlook for Windows (replacing classic Outlook over the coming years) takes a different approach: it's a thin web client that talks to Exchange via Microsoft Graph, with much smaller local cache footprint. Cache…

Solving Microsoft 365 · www.solvingmicrosoft365.com/guides/outlook-cached-mode-and-ost-files

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04

What to do today

.ost files aren't going extinct soon, but their day-to-day relevance is shrinking.

Solving Microsoft 365 · www.solvingmicrosoft365.com/guides/outlook-cached-mode-and-ost-files

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