DMARC reject: no alignment
Your DMARC policy is `p=reject` and neither SPF nor DKIM alignment passed. Receivers are instructed to reject the message outright.
This is the worst case. Mail is rejected at the SMTP level — your users see bounces, not Junk. Senders get NDRs. The business impact is immediate and visible.
What causes it
- A sending service's SPF record passes against their domain, not yours — SPF alignment requires the Return-Path domain to match the From domain.
- DKIM is signing with the service's domain (e.g., d=mailgun.org) instead of yours.
- You enabled DMARC
p=rejectbefore completing SPF and DKIM setup for all your senders.
How to fix it
Step 1: Downgrade DMARC to p=quarantine or p=none temporarily
Give yourself breathing room while you diagnose. p=none still gets you the DMARC reports (via rua=) so you can see what's misaligned without rejecting live mail.
Step 2: Fix alignment
For every sender, configure DKIM to sign with your own domain. Example: for Mailgun, set up a custom domain with your own DKIM selector so d= matches your From domain. Same for SendGrid (sender authentication), Postmark (verified domain), etc.
Step 3: Verify with DMARC aggregate reports
Add a rua= tag to your DMARC record and parse the resulting XML (or use a service like Postmark DMARC Digests, Valimail, or dmarcian). Only re-enable p=reject once reports show 100% alignment for a week.
Fixed it? Run a fresh test to confirm.
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