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Email verifiers

Migrate from Kickbox

This guide maps the Kickbox API v2 (single verification, batch verification, and balance) to the Tomba Email Verifier and bulk verifier jobs. Kickbox API behavior checked on 2026-09-29 against Kickbox's official client libraries on GitHub.

Before you begin

• Get your API key (ta_…) and secret (ts_…); see Authentication.
• Check what a verification costs in Credit costs and your plan's throttling in Limits by plan.
• Set your HTTP client timeout to at least 180 seconds. Tomba returns the finished result in the response.

Endpoint mapping

Replace the host api.kickbox.com with api.tomba.io.

Authentication changes

Kickbox's client libraries send the key as Authorization: token <key>. Tomba needs two headers, X-Tomba-Key and X-Tomba-Secret:

Code
# Kickbox
curl "https://api.kickbox.com/v2/verify?email=jane.doe@stripe.com" \
  -H "Authorization: token $KICKBOX_API_KEY"

# Tomba
curl "https://api.tomba.io/v1/email-verifier?email=jane.doe@stripe.com" \
  -H "X-Tomba-Key: $TOMBA_API_KEY" \
  -H "X-Tomba-Secret: $TOMBA_SECRET_KEY"

Tomba API keys expire; plan their rotation with Key expiry.

Parameter mapping

Response field mapping

Kickbox returns a flat object. Tomba nests the checks in data.email and lists the public pages where the address appears in data.sources. Field definitions are in Email verifier response.

Tomba also returns block, greylisted, gibberish, regex, mx_check, mx.records, smtp_provider, and whois, which have no Kickbox counterpart.

Status mapping

Branch on status rather than result: Tomba's unknown status carries the result risky, and a disposable address has an empty result. Compare status case-insensitively. Each value is defined in Status values.

Error mapping

Both APIs signal failures with HTTP status codes. Tomba's error body is an errors object with type, message, and code.

Tomba also returns 429 rate_limit when you exceed your plan's rate limits (retry after Retry-After; see Handle 429 responses), 408 proxy_error when the mailbox check fails, and 451 claimed_email when the owner of the address asked Tomba to stop processing it. Remove 451 addresses from your list. Error responses don't consume credits; every type is listed in Errors.

Bulk and async jobs

Code
curl -X POST "https://api.tomba.io/v1/bulk/verifier" \
  -H "X-Tomba-Key: $TOMBA_API_KEY" \
  -H "X-Tomba-Secret: $TOMBA_SECRET_KEY" \
  -H "Content-Type: application/json" \
  -d '{"name": "Newsletter list", "list": "jane.doe@stripe.com\njohn.smith@shopify.com"}'

The launch, progress, and download requests are shown in Lifecycle. Row limits and daily job limits are in Limits, and a job is charged when you first download its results; see Billing.

Code example

This function replaces a call to /v2/verify and returns Kickbox's field names for the values Tomba provides. It needs Node.js 18 or later.

Code
const TOMBA_HEADERS = {
    "X-Tomba-Key": process.env.TOMBA_API_KEY,
    "X-Tomba-Secret": process.env.TOMBA_SECRET_KEY,
};

// Tomba status -> Kickbox result
const RESULTS = {
    valid: "deliverable",
    invalid: "undeliverable",
    accept_all: "risky",
    disposable: "risky",
    unknown: "unknown",
};

async function verify(email) {
    const url = new URL("https://api.tomba.io/v1/email-verifier");
    url.searchParams.set("email", email);
    const res = await fetch(url, { headers: TOMBA_HEADERS });
    const body = await res.json();
    if (body.errors) {
        throw new Error(
            `${res.status} ${body.errors.type}: ${body.errors.message}`,
        );
    }

    const check = body.data.email;
    return {
        result: RESULTS[check.status.toLowerCase()] ?? "unknown",
        email: check.email || email,
        free: check.webmail,
        disposable: check.disposable,
        accept_all: check.accept_all,
        success: true,
    };
}

console.log(await verify("jane.doe@stripe.com"));

Cutover checklist

1. Store the Tomba key and secret as TOMBA_API_KEY and TOMBA_SECRET_KEY, and send them as X-Tomba-Key and X-Tomba-Secret.
2. Point single verifications at GET https://api.tomba.io/v1/email-verifier, drop the timeout parameter, and set a client timeout of at least 180 seconds.
3. Read results from data.email and translate result and reason with the status mapping, comparing status case-insensitively.
4. Handle 402 where you handled 403 Insufficient balance, retry 429 after Retry-After, and drop addresses that return 451.
5. Replace batches with verifier bulk jobs: create, launch, poll /progress, and download the CSV.
6. Verify the same sample list with both services and compare the mapped results before you switch production traffic.