I have email routing setup to forward to iCloud email. A number of emails appear to be being rejected by iCloud:
Unknown error: permanent error (554): 5.7.1 Your message was rejected due to alertshub.ft.com’s DMARC policy. See Postmaster information for iCloud Mail - Apple Support for info
DKIM and SPF are both shown as passing.
This appears to happen across a number of different email sources and only appears to happen when Cloudflare email routing is an intermediary