Quality scores & verdicts
How MailSentry calculates the 0-100 quality score, what each verdict means, and the exact penalty weights.
How scoring works
Every email starts at 100. Each validation layer that finds an issue applies a penalty. The final score is what's left after all deductions.
Three checks are instant fails — they drop the score to 0 immediately:
- Invalid syntax (the address can't be parsed)
- Domain typo detected (the domain is a misspelling)
- Provider format violation (e.g., Gmail-specific rules broken)
- System address (noreply@, postmaster@, abuse@)
Everything else applies weighted deductions that stack. An email that's role-based and on a catch-all domain gets both penalties.
Penalty weights
Hard failures set the score to zero immediately — no other penalties apply:
| Signal | Penalty |
|---|---|
| Invalid syntax | Score = 0 |
| Domain typo detected | Score = 0 |
| Provider format violation (e.g., Gmail-specific rules) | Score = 0 |
| System address (noreply@, postmaster@, abuse@) | Score = 0 |
Everything else applies weighted deductions that stack:
| Signal | Penalty |
|---|---|
| SMTP: mailbox doesn't exist | -75 |
| Role-based address (info@, sales@, support@) | -45 |
| No MX records | -40 |
| Disposable email domain | -35 |
| Gibberish local part | -35 to -70 |
| SMTP inconclusive (timeout or greylisting) | -30 |
| Free provider with plus-addressing | -30 |
| Free provider with 3+ dots | -30 |
| Toxic/abuse-associated address | -25 |
| Garbled identifier (e.g., randomxyz123abc@) | -25 |
| Spam trap pattern | -20 |
| Suspicious pattern (test@, keyboard walks) | -15 to -30 |
| New domain (under 30 days) | -15 |
| Catch-all domain | -5 to -35 |
| SMTP inconclusive + no MX (compound) | -10 additional |
Verdicts
The score maps to a verdict — a plain-language label you can use in your application logic:
| Score range | Verdict | Recommendation |
|---|---|---|
| 90-100 | valid | Safe to send |
| 60-89 | caution | Send with caution — some risk of bounce |
| 30-59 | risky | High risk — we recommend not sending |
| 0-29 | invalid | Do not send |
Score consistency
SMTP results can vary between checks — a server might timeout once and respond the next time. To prevent this from confusing your application, MailSentry pins scores for 30 days. If you verify the same email twice within that window, you'll get the same score.
After 30 days, the pin expires and the email is checked fresh. This balances consistency with accuracy — enough time for your application logic to stay stable, but not so long that stale results persist.