MailScout Trust Score Explained — What Your Email Score Means
A 0-100 rating that tells you how trustworthy an email address really is
The trust score is MailScout's signature metric. It distills the output of seven verification engines into a single number you can act on. Whether you're cleaning a mailing list, vetting signups, or investigating a suspicious address, the score gives you instant context.
The algorithm uses a veto-plus-bonus model. First, hard failures apply penalties: invalid syntax (-100), no MX records (-80), SMTP rejection (-60), RBL listing (-40). Then, positive signals add points: valid SMTP handshake (+30), SPF/DMARC/DKIM present (+15 each), domain age > 2 years (+10), known ESP provider (+10), Gravatar found (+5). The final score is clamped to 0-100. This means a single critical failure can drive the score to zero, while multiple positive signals build toward 100.
| Range | Label | What It Means | |
|---|---|---|---|
| High Confidence | 80-100 | Highly Trusted | Valid SMTP, strong security config, old domain, no blacklist. Safe to send. |
| Trusted | 60-79 | Trusted | Valid SMTP with decent security. Good for most use cases. |
| Partial | 50-59 | Partially Verified | Syntax and DNS check out, but SMTP was inconclusive or security is weak. Use caution. |
| Doubtful | 30-49 | Doubtful | Catch-all domain, missing security records, or young domain. Higher bounce risk. |
| Risky | 15-29 | Risky | SMTP failed or domain is on a blacklist. High probability of bounce or spam trap. |
| Untrusted | 0-14 | Untrusted | Invalid syntax, no MX records, or hard SMTP rejection. Do not send. |
- SMTP Validation — The heaviest weight. A valid 250 response adds +30; a 550 rejection subtracts -60.
- DNS & MX Records — Valid MX records are baseline. Missing MX or null MX (RFC 7505) is a hard fail.
- Domain Security — SPF, DMARC, and DKIM each contribute +15 when present and correctly configured.
- Domain Age — Domains registered for over 2 years get a +10 bonus. Recently registered domains are penalized.
- Blacklist Status — Presence on Spamhaus, Barracuda, or other RBLs subtracts -40. This is a strong negative signal.
- Email Pattern — Role-based prefixes (admin@, info@, support@) and random strings slightly reduce the score.
john.smith@gmail.com → Score 92 (valid SMTP, SPF/DMARC present, old domain, known ESP). test@nonexistent-domain-12345.com → Score 0 (no MX records, invalid domain). admin@catchall-company.io → Score 45 (catch-all detected, no individual confirmation possible). newsletter@spam-listed.biz → Score 18 (RBL listed, SMTP rejected).
The trust score is a guidance tool, not a guarantee. A high score means the address is likely valid and reputable, but email behavior can change. Always combine scoring with engagement metrics (opens, clicks) for the best list hygiene strategy.