I mean, the volume is absolutely an issue but it looks like they failed to configure DKIM/DMARC/SPF and this is a lazy policy end run around a gap in technical knowledge. I'm not surprised, but it is a bit amusing.
If you insist on running Meta's spyware on your devices you can also use a service like nextDNS to block trackers at the device DNS level: https://apple.nextdns.io