Predownload Emails For Fast Viewing

Hi - I just installed eM Client and I made sure to select the option for Downloading emails for searching the body, etc.

My Internet isn’t the fastest so I thought this (the above) would mean that all the emails were downloaded to eM Client and I could browse more easily.

Currently I have the problem where I go to any email (an old email that hasn’t been opened on eM Client which was imported in) and then I have to wait for 5 seconds for the email to load (loading bar at the top) and then show… Which is making quickly going through and deleting a load of old emails quite problematic.

I thought maybe I just need to wait for eM Client to download all the emails but I am not sure if that is actually happening because I have tried both latest and oldest ones in the Inbox/All Mail but I still have to wait for any email, so clearly nothing has ‘downloaded’ (pre-downloaded) as I had hoped. Is this possible? Thank you