DMARC collects no reports
With no rua= address you get no aggregate reports, so you cannot see who is sending as your domain or whether your own mail is passing. You are enforcing a policy blind.
_dmarc.example.comv=DMARC1;p=reject;sp=reject;adkim=s;aspf=s; rua=mailto:dmarc@example.com
Before you publish: The mailbox must exist and will receive daily XML attachments from mailbox providers.