I need to periodically check gmail spam because almost all legit emails from small business (order confirmations, support requests etc) with dedicated email ser

I need to periodically check gmail spam because almost all legit emails from small business (order confirmations, support requests etc) with dedicated email server fall in there. I explicitly mark them as not Spam but it's still not working. All of those servers use TLS, DKIM, SPF etc. And my spam folder contains almost none actual spam letters, they just stop arriving a few years ago dispite my email address is very public.