Validation Levels
Cleanmails offers two verification levels with different speed/accuracy tradeoffs.
Level 1 — Fast Analysis
Near-instant checks that don't require SMTP connections:
| Check | Speed | What It Does |
|---|---|---|
| Syntax | <1ms | RFC-compliant regex validation |
| MX Lookup | ~50ms | Verifies domain has mail servers |
| Disposable | <1ms | Checks against 126,000+ disposable domains |
| Role Account | <1ms | Detects info@, admin@, support@, etc. |
| Free Provider | <1ms | Flags Gmail, Yahoo, Outlook, etc. |
| Domain Suggestion | ~5ms | Levenshtein distance typo correction |
Speed: 10,000+ emails/minute
Use when: You need fast filtering, don't need deliverability confirmation, or port 25 is blocked.
Level 2 — Deep SMTP Handshake
Everything in Level 1, plus real SMTP verification:
| Check | Speed | What It Does |
|---|---|---|
| SMTP Connect | 1-10s | Connects to recipient's mail server on port 25 |
| RCPT TO | 1-5s | Tests if the specific mailbox exists |
| Catch-All | 2-5s | Tests random addresses to detect accept-all domains |
| Google API | 1-3s | GXLU endpoint for Gmail verification |
| Yahoo API | 2-5s | Signup validation for Yahoo addresses |
| Outlook API | 1-3s | GetSelfSignedKey for Microsoft addresses |
Speed: 50-100 emails/second (network dependent)
Accuracy: >98.5%
Use when: You need to confirm deliverability before sending campaigns. Required for cleaning lists before outreach.
Choosing a Level
| Scenario | Recommended Level |
|---|---|
| Signup form validation | Level 1 (instant feedback) |
| Pre-campaign list cleaning | Level 2 (maximum accuracy) |
| Port 25 blocked on your server | Level 1 (SMTP won't work) |
| Large list (>50k) quick filter | Level 1 first, then Level 2 on valid results |
| CRM integration (real-time) | Level 1 (fast response) |
Catch-All Domains
Some domains accept all addresses (catch-all). Level 2 detects these by sending RCPT TO with random addresses. If the server accepts random addresses, the domain is marked as catch-all and individual deliverability can't be confirmed — result is unknown.
For bulk jobs, once a domain is identified as catch-all, all remaining emails on that domain skip the SMTP check (optimization).