## TL;DR

Invoices emailed from an unverified domain fail SPF and land in spam: receiving servers cannot verify the sender, so they quarantine the mail. Authenticate the sending domain with SPF, DKIM, and DMARC before any invoice mail goes out, warm the domain reputation gradually, and monitor delivery. Never send financial documents from an unauthenticated domain.

```text
agent emailed invoices from an unverified domain: SPF fail, all mail to spam
```

## Use this when

- Invoice emails from an unverified domain go to spam
- SPF fails on outgoing invoice mail
- You are setting up a new sending domain

## Not for this skill when

- Mail is authenticated but still filtered (content or reputation issue)
- The recipient's server blocks you for another reason
- You are debugging the invoice PDF rather than delivery

## Steps

1. Confirm the failure: check SPF/DKIM/DMARC results on a sample invoice email.
   Expected: The authentication gap is proven.
2. Publish SPF, DKIM, and DMARC records for the sending domain.
   Expected: The domain is authenticated.
3. Verify the records with a mail tester and confirm alignment.
   Expected: Authentication passes.
4. Re-send the affected invoices from the authenticated domain.
   Expected: Customers receive them.
5. Set up ongoing monitoring: DMARC reports and delivery rates.
   Expected: Regressions are visible.
6. Warm new domains gradually; do not blast the full invoice volume on day one.
   Expected: Reputation builds safely.

## Tool compatibility

DNS (SPF, DKIM, DMARC records); email providers; invoice delivery flows.

## Variant phrasings

### invoice emails spam SPF fail

The symptom phrased directly.

### authenticate sending domain invoices

The fix as an action.

### unverified domain invoice delivery

The configuration angle.

## Why it happens

Receiving mail servers treat unauthenticated mail as suspicious by default, and financial documents like invoices get extra scrutiny: an SPF fail is enough to route them to spam or reject them outright. The agent did everything right except the domain authentication, so customers never saw the invoices and payments stalled. SPF, DKIM, and DMARC together prove the mail genuinely comes from your domain; without them you are indistinguishable from a phisher. Domain authentication is therefore a prerequisite for invoice email, not a deliverability optimization.

## Edge cases / pitfalls

- SPF has a 10-DNS-lookup limit; flatten includes or the record breaks.
- DMARC policy should start at none (monitoring) before moving to quarantine or reject.
- Subdomains need their own authentication story; authenticating the apex does not cover everything.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_CxJzMDOqY9Zy4F0-p21dSQ