Thanks for the extensive response but with around 62k mails a day, on each MX, I think pre-queue filtering requires too much RAM. It's been made clear to me, t

Thanks for the extensive response but with around 62k mails a day, on each MX, I think pre-queue filtering requires too much RAM. It's been made clear to me, thanks to this thread, that I first and foremost need to explore greylisting in postfix before mail is passed to the proxy_filter. Secondly that I should explore dspam and rspamd as faster alternatives to SA.