Legitimate emails going to junk

Outlook is constantly sending legitimate emails to the junk folder. These are usually from new senders, so I can't fix it by adding their addresses—I don't know who they are ahead of time. I have tried to create rules to move things out of the junk folder automatically, or prevent emails with attachments from going to that folder, but they have no effect.

I don't mind checking the junk folder, but the problem is the Microsoft deletes junk emails after 10 days. Can I either get rid of the junk email folder (I'm happy to sort the emails myself), or have this time extended? This unwanted, unnecessary feature causes many more problems than it solves.