Email history sent to POP folder without warning. When I try to change settings, can’t connect to Outlook. When I click on gear icon, nothing under ‘Managing History’ helps.

At the bottom of the screen, a heading warns a program may transfer emails to POP folder but I could click on 'change settings' to stop this. When I click on 'change settings', I'm unable to connect to Outlook. Reading similar if not identical problems on the question board, I clicked on the gear icon but under Managing Account there's nothing  noted where I can change the program re Pop folder. My email history has stored stuff for years. Why the sudden change? Read emails now remain only a couple of days and are suddenly in the POP folder.  How long will they remain in the POP folder or will they be somehow deleted from there as well? That'd be a catastrophe for me. Suggestions?