Combines tier-1 deliverability (syntax, DNS/MX, SMTP) with tier-2 risk signals. Score 0 = best, 100 = worst. The grade is separate from the status: status is valid (passed SMTP), invalid (failed a check), unknown (no SMTP response) or risky (spam trap, screamer, DND, organisation domain, honeypot, role account, disposable or catch-all).
| Grade | Score band | What it means |
|---|---|---|
| A+ | 0–9 | Clean deliverable address with no risk signals. |
| A | 10–19 | Deliverable, very low risk. Safe to send. |
| B+ | 20–29 | Deliverable but one weak signal (e.g. catch-all domain). |
| B | 30–39 | Mostly clean, possibly on suppression-adjacent list. |
| C | 40–59 | Mixed signals — review before sending. |
| D | 60–79 | Likely deliverability problems. Use cautiously. |
| F | 80–100 | Undeliverable, suppressed, or hard-failed. |
Signals that feed this channel’s score
- Syntax (RFC 5322)
- Domain MX records
- SMTP handshake (skipped in dev / when port 25 is blocked)
- Bounce DB match (informational)
- Spam-trap list match
- Role-account flag (admin@, support@, …)
- Disposable / temp-mail domain
- Organisation domain — government, military, education, large corporate (risky)
- Screamer / DND / honeypot (tenant suppression reasons)
