[BSDobelix]

I like rspamd much more (performance and redis) than SpamAssassin, and as you mentioned:

-https://www.mail-tester.com

-https://www.learndmarc.com

-https://mecsa.jrc.ec.europa.eu/en/

Are exellent tool's to check your "deliverability".

[CableNinja]

Suprised to not see https://mxtoolbox.com in this list too

[BSDobelix]

Truetrue sorry, I forgot ;)