I have hit the common issue of my DO IP address being blocked by hotmail, after 10+ years of trouble free usage!

They are completely unhelpful on why this is happening now so I am trying to sort it myself.

I have postfix configured to reject all unknownsenderdomain and I have noticed a lot of spam attempts from hotmail addresses in the logs. I wonder if there is a form of backscatter going on because I am then sending rejects?

Rather than send any sort of reject, can I configure postfix to silently discard the email and not send any reply?
eg; I have ‘rejectunknownsender_domain’ in main.cf