# Spaw vs Mailboxlayer: email verification API comparison

How Spaw and Mailboxlayer compare on pricing, billing rules, verification depth and limits, from Mailboxlayer's public pages checked on 2026-09-03. Corrections: support@spaw.co.

| | Spaw | Mailboxlayer |
| --- | --- | --- |
| Pricing model | Pay-as-you-go credit packs bought through Stripe Checkout; no subscription, credits never expire | Monthly or yearly subscription with a request quota per plan and per-request overage |
| Free tier | 10 free credits every month, no card required | 100 requests a month |
| Price per 1,000 at about 10k | $7.80 (Growth pack: 5,000 credits for $39) | $3.00 (Basic: 5,000 requests for $14.99 a month, overage $0.012 a request; Professional Plus: 50,000 for $74.99, $1.50 per 1,000) |
| Price per 1,000 at about 100k | $4.99 (Volume pack: 100,000 credits for $499) | $1.50 to $1.00 (Professional Plus: 50,000 requests for $74.99; Enterprise Plus: 250,000 for $249.99) |
| Unknown or catch-all results billed | Yes, by verdict: a deliverable or risky answer costs 1 credit even when the mailbox is unconfirmed; the automatic re-checks are free | Yes |
| Undeliverable results billed | No, undeliverable verdicts are always free | Yes |
| SMTP mailbox check | Yes | Yes |
| Catch-all handling | A catch-all answer is remembered per domain for 7 days, and every unconfirmed mailbox carries a published 0 to 100 mailbox_confidence estimate | Catch-all detection from the Basic plan up; every request counts against the quota |
| Bulk limit | 100,000 addresses per bulk job, with an HMAC-signed completion webhook | Bulk endpoint: 25 emails per request on Professional Plus, 100 on Enterprise Plus |
| Batch API | 50 addresses per synchronous request, probes sent concurrently | 25 or 100 emails per request depending on plan |
| Rate limit | 5 requests per second per key | not published |
| Official SDKs | Python, Node.js, PHP | not published |
| Data retention | Lookup history kept for 30 days, then pruned; test addresses are never logged | not published |

## When Mailboxlayer fits better

Developers who prefer a flat monthly quota and already use other apilayer APIs.

- SMTP check, MX records, syntax and typo validation, free and disposable databases on paid plans
- 256-bit HTTPS encryption listed for paid plans
- Part of the apilayer marketplace

## When Spaw fits better

Developers who want one flat price per answered lookup, a transparent risk score, and an API that documents every field.

- Mailboxlayer counts every request against a monthly quota; Spaw bills only answered lookups and leaves undeliverable verdicts free
- Spaw's bulk jobs take 100,000 addresses; mailboxlayer's bulk endpoint takes 25 or 100 per request depending on plan
- Spaw includes the SMTP handshake on every lookup including the free monthly grant; mailboxlayer lists the SMTP check on its paid plans
- At high volume mailboxlayer's quota price of $1.00 to $1.50 per 1,000 is below Spaw's $4.99

## Questions

**Does Spaw charge for catch-all or unknown results?** Spaw bills per answer, not per probe outcome: a lookup that comes back deliverable or risky costs 1 credit even when the mailbox could not be confirmed, for example on a catch-all domain or after greylisting. Undeliverable verdicts, invalid input, repeats within 7 days and the automatic re-checks behind callback_url are free. Mailboxlayer counts them according to its public pages.

**Can I move a list from Mailboxlayer to Spaw?** Yes. Upload the CSV to the dashboard or POST it to the bulk endpoint; Spaw keeps your columns, adds the verdict columns, and lets you download only the deliverable, risky or undeliverable rows. Addresses that come back undeliverable join your suppression list so later runs skip them for free.

**Is there a free tier?** Every Spaw account receives 10 free credits at the start of each month with no card on file, and unused credits accumulate. Mailboxlayer offers: 100 requests a month.

## Sources (checked 2026-09-03)

- [Mailboxlayer product and pricing](https://mailboxlayer.com/product)

Mailboxlayer is a trademark of its owner. Spaw is not affiliated with it.

Reference: https://spaw.co/compare/mailboxlayer