I can agree with everyone here, self hosting mail at this point is pointless. You are going to spend so much of your time reaching out to be pulled off of blacklists only to be added right back onto another. It’s a vicious cycle unfortunately, and than just wait until you get added to Barracudas or Proofpoints naughty list… you may as well start over at that point.
3 Proxmox nodes 2 SFF Dell Optiplex (i5 with 32gb RAM) 1 Nuc (i7 with 64gb RAM)
1 Truenas host (old gaming PC i5 with 64gb RAM and 8TB ZFS pool
pfSense appliance for firewall