Where does the modern Outlook store its cache

Hi,

Yes, what you are seeing is expected with the new Outlook for Windows. Unlike classic Outlook, new Outlook does not use Cached Exchange Mode. Microsoft specifically notes that Cached Exchange Mode is not available in new Outlook for Windows. In classic Outlook, Cached Exchange Mode is the feature that maintains a local copy of an Exchange/Microsoft 365 mailbox, typically in an .ost file.

Microsoft reference: Turn on Cached Exchange Mode | Microsoft Support

New Outlook instead has its own Offline access feature. When Offline access is enabled, new Outlook saves copies of supported mailbox data, including emails, calendar events, and contacts (People), on the device so that they remain available without an Internet connection and can also improve performance while online.

You can review the supported offline settings in new Outlook under: Settings > General > Offline

From there, you can control:

• Whether Offline access is enabled. It is enabled by default.
• Which folders are saved locally.
• How many days of email are saved locally: 7, 30, 90, or 180 days. The default is 30 days.

Microsoft documents these settings here: How to work offline in Outlook for Windows | Microsoft Support

Regarding the actual cache location, the Microsoft documentation above describes how new Outlook stores data locally for Offline access, but it does not document a user-manageable cache file or physical cache path equivalent to the .ost file used by classic Outlook. Therefore, I would not recommend treating the new Outlook offline data as an OST/PST-style cache or manually modifying its local application files.

PST files are slightly different from the mailbox cache. New Outlook now supports certain PST operations, so the absence of an automatically generated PST should not be taken to mean that PST files are unsupported. Microsoft currently documents the available PST functionality in new Outlook here: Open and find items in an Outlook Data File (.pst) | Microsoft Support

So, an Exchange/Microsoft 365 mailbox in new Outlook does not use the traditional Cached Exchange Mode/OST model. New Outlook manages its offline mailbox data through its own Offline access feature instead. If you can share what you are trying to accomplish by locating the cache (for example, checking local storage usage or understanding offline availability), I can point you to the supported option for that purpose.