How to clear Outlook cache

Step 1: Press the Windows + R keys simultaneously to open the Run dialog box.
Then type the following path into the Run box and press Enter.
 


Step 2: This will open the RoamCache folder containing the cache files associated with your Outlook profile.
Click anywhere within the folder, press Ctrl + A to select all files, and then press the Delete key to remove them.
Alternatively, you can right-click the selection and choose the Delete option from the context menu.

After clearing the cache, restart Outlook again. It will rebuild the necessary cache files from scratch.
This way, you can delete the excessive cache that may be hindering Outlook’s functionality and restore its syncing capabilities.

Credit : https://www.ablebits.com/office-addins-blog/clear-outlook-cache/