Short answer
Not with a phased approach. FirstNet identifies and authenticates every legitimate sending source before enforcement, moves your policy through quarantine with rollback guardrails, and only then reaches reject, so legitimate marketing and transactional email keeps flowing.
In detail
The managed journey works like this:
- FirstNet publishes a monitoring-only DMARC record (p=none) and collects reports from receiving mail providers
- Every sending source is classified as legitimate, a forwarder or unauthorised; most organisations find 15 to 40 sources, including marketing platforms, ERP and finance systems
- FirstNet engineers specify SPF and DKIM alignment for each legitimate platform, your administrators make the changes, and FirstNet validates them
- Policy moves to p=quarantine, then p=reject, with go or no-go reviews at each step
- Monthly managed-service reviews pick up new senders, such as a newly adopted marketing tool, so they can be authenticated
Moving to p=reject too quickly is what breaks email, because most organisations have more legitimate senders than they realise. Gating each step on full source authentication removes that risk.
Engage your marketing platform owners early, because their changes set the pace.
Source: FirstNet Email Security & Threat Protection service page →
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