Understanding Email Risk Scores

The Email Risk Score is a send-safety grade. It answers one question: if you send to this address, how likely is it to land in an inbox rather than bounce, hit a spam trap, or damage your sending reputation? It is not a confidence score for whether the address belongs to the person you looked up.

The most common misreading. An A does not mean “we are certain this is their address.” It means the mailbox is live and safe to send to. A C or F does not mean the match is wrong — it means we can’t confirm deliverability. Grade the send, not the identity.

What the score does and doesn’t measure

The score tells you	The score does not tell you
Whether the mailbox exists and accepts mail	Whether the address belongs to the person you searched for
Whether a past send to it landed without bouncing	Whether the person still works at that company
Whether the address has been seen as a spam trap or complaint source	How current the underlying record is
Whether the domain accepts everything (catch-all), making deliverability unknowable	How the address was sourced or derived

Identity accuracy comes from the tool you called, not from this field. search_business_email_by_name, for example, matched a name against a company domain; the risk score then grades the resulting address for sending. The two are independent — a correctly matched address can be catch-all (C), and a deliverable address (A) can belong to a person who has since changed jobs. Read last_validated_at alongside the grade for freshness.

Why the grade exists

In spring 2026, Microsoft began blocking SMTP-based validation checks. Third-party validators (NeverBounce, ZeroBounce, and others) consequently started marking fully configured, deliverable inboxes as “invalid” — addresses that receive mail perfectly well. A single vendor verdict is no longer a reliable send/don’t-send signal. The Email Risk Score is computed from everything MoltSets holds about the address — live validation, its own validation history, real engagement, and spam sightings — rather than from one SMTP probe.

The grades

Score	What it means	How it’s earned	Recommendation
A	Validated deliverable	Confirmed `valid` at validation time, or a prior validation whose deliverable flag holds	Send
B	Known engagement, deliverability not re-validated	A recorded open, click, or order — proof a past send reached the inbox without bouncing	Probably send
C	Catch-all — deliverability unknowable	The receiving server accepts mail for every address at that domain, so acceptance proves nothing	Your call
D	Hard negative	A standing spam-trap, abuse, or do-not-mail verdict, or a spam/complaint sighting in the last 6 months	Don’t send
F	No signal	No validation record and no engagement history — nothing is known either way	Your call

Two points that trip people up:

F is not a bad grade, and D is not a strong one. F means no evidence; D means negative evidence. They are opposite ends of what we know, not neighbouring tiers.
C is a property of the domain, not the person. A catch-all server accepts everything, so no validator — ours or anyone else’s — can confirm an individual mailbox behind it.

Precedence when signals disagree: D > A > B > C > F. A hard negative outranks everything, including a fresh deliverable verdict. A live catch-all verdict outranks older date-based evidence, because the server-level unknowable is the more current fact.

How it reaches you

The grade is appended to every email a tool returns, next to the validation date. The one exception is reverse_email_lookup: it doesn’t grade the address you pass in, since you supplied it.

{
  "results": {
    "email": "john.smith@example.com",
    "risk_score": "A",
    "last_validated_at": "2026-08-25"
  },
  "status": "ok"
}

Tools that return more than one address carry a companion field per address — business_email_risk_score, personal_email_risk_score, and a personal_emails_risk_score array index-aligned with personal_emails. search_people rows carry business_email_risk_score alongside each contact. reverse_email_lookup carries work_email_confirmed_risk_score for the work email it finds on file. Addresses that fail validation outright are dropped before they reach you rather than returned with a low grade — which is why most payloads skew toward A, B, and C. A lookup whose only address was dropped comes back as a not_found, and costs nothing. Scoring is best-effort and never fails a call: if a scoring lookup is degraded, the risk_score field is simply absent. Treat a missing grade like F — unknown, not safe.

Best practices

Treat the grade as a filter, not a guarantee. A “Send” recommendation lowers risk; it doesn’t eliminate it. Pair it with your own domain reputation and list hygiene.

By grade

Grade	Best practice
A	Safe to send immediately. Strongest deliverability signal available.
B	Solid for regular sends. For reputation-sensitive campaigns (cold outreach on a new domain), send a smaller batch before scaling.
C	Deliverability can’t be confirmed. Segment separately from A/B, warm with lower volume, watch engagement closely, and suppress non-responders after 1–2 attempts.
D	Never send. The fastest way to trip spam traps and damage sender reputation for the whole list.
F	Unknown risk, not safe. Re-verify before sending, or route into the same cautious treatment as C.

General sending hygiene

Suppress D at the list level automatically rather than relying on manual review
Monitor bounce rate by grade over time to confirm the scoring holds up for your use case
Warm up new domains regardless of grade when sending cold outreach
Re-score periodically. Deliverability decays — job changes, inbox closures — and the grade reflects what was known at the time of the call, which last_validated_at dates for you

Getting Valid Emails

Which email endpoint to call, and how to avoid paying twice.

Phone Number Validation

The phone-side equivalent, and how to read its validation date.

Getting Started

MoltSets' Data

Use Cases

Best Practices

Integrations

What the score does and doesn’t measure

Why the grade exists

The grades

How it reaches you

Best practices

By grade

General sending hygiene

Getting Valid Emails

Phone Number Validation

​What the score does and doesn’t measure

​Why the grade exists

​The grades

​How it reaches you

​Best practices

​By grade

​General sending hygiene

​Related

Getting Valid Emails

Phone Number Validation

What the score does and doesn’t measure

Why the grade exists

The grades

How it reaches you

Best practices

By grade

General sending hygiene

Related