What are the most common reasons a DMARC DNS record fails to be recognized by receivers?
Receivers most often fail to recognize a DMARC DNS record because of syntax or tag-value errors (for example, missing v=DMARC1 or invalid p=), wrong DNS type or placement (DMARC must be a TXT at _dmarc.yourdomain), provider UI formatting or TXT-length mishandling, propagation/TTL and negative caching, DNSSEC or delegation problems, invalid or unverified rua/ruf URIs, duplicate/conflicting…
