My practice is to capture the raw stuff on the right hand page and then keep the left hand page for later clarification or distillation. Thus a quick flick through a notebook shows which pages got developed further than the daily flux.
the second problem, because its my original thought, I'm naturally attached and biased to my precious thought in that moment. The same thought could feel dumb or obvious or wrong next week. But right then it feels like I've stumbled upon something so insightful. So I need to write it down to revisit.
I've now distributed manila folders with 5-10 blank college ruled sheets of paper across different rooms in my home. I'm never too far from a blank piece of paper.
in the moment, I write it down on a sheet. Fold it and put it in my pocket. Its with me the entire day to review, add on or scratch off. It ends either in the bin or the binder at my desk. As the binder gets thick, i trash or consolidate to keep it thin. The really insightful ideas as far too few for a $2 binder.
Works way better than any other form of capturing insights. As i look through, my binder has so many backs of mailer's i've received and scribbled on. cant figure why.
Is your mailbox a short walk from where you normally work? Walks have been credited for the assist in idea generation from Aristotle to Nietzsche (and beyond).
I personally just keep a little pocket notebook and a couple pens on my person at all times. That replaces the need for the distributed folders of your system. Every week I go through and add them to either my paper notebook or my digital notes.
I don’t really trash the “bad” ideas either since my notebook is bound. I try to be neither precious with the good ideas nor embarrassed of the bad. I treat them all as just a record of thoughts.
on that note, the small whiteboard right next to my desk (at home) was a great idea too