How fast is a single check?

Most answers return in a few seconds. Slow servers return processing after about 12 seconds (about 25 seconds for a batch).

How do I handle processing?

Call GET /api-validation/single/result with the same address until the final status arrives, usually within a minute or two. Asking again within 30 minutes doesn't use another credit.

Use batch for up to 50 addresses in one JSON request. Use bulk for files: upload a CSV up to 50 MB, poll the job status, then download the results.

What are the rate limits?

Per API key, each minute: 100 single checks (shared with collecting results), 10 batch requests, 10 bulk uploads, 120 bulk status checks and 30 downloads. Your organisation as a whole gets three keys' worth, for example 300 single checks a minute. Going over returns HTTP 429 with a Retry-After header.

Yes. Create a test API key (it starts with sc_test_) and every endpoint returns fixed sandbox results without using credits: one address for each result, slow checks to practise polling, simulated 429 and 500 errors, bulk jobs of up to 1,000 rows, and webhooks marked livemode false. The sandbox page in the docs lists every address. Then use your 200 free credits on real addresses before you go live.

An email verification API that tells you why

Send an address, get back a category, a plain reason and a typo suggestion. One endpoint for real time, two for lists.

Start free with 200 credits See how it works

Show me

simplecold.com / api / v1 / api-validation / single

curl "https://simplecold.com/api/v1/api-validation/[email protected]" \
  -H "Authorization: Bearer <key>"

const res = await fetch(
  "https://simplecold.com/api/v1/api-validation/[email protected]",
  { headers: { Authorization: `Bearer ${process.env.SIMPLECOLD_KEY}` } }
);
const result = await res.json();

import requests

res = requests.get(
    "https://simplecold.com/api/v1/api-validation/single",
    params={"email": "[email protected]"},
    headers={"Authorization": f"Bearer {KEY}"},
)
result = res.json()

200 OK · example response

{
  "email": "[email protected]",
  "status": "possible_typo",
  "category": "undeliverable",
  "statusMessage": "Possible typo. Did you mean [email protected]?",
  "failType": "permanent",
  "suggestion": "[email protected]"
}

Six checks on every address
A plain reason with every result
Slow servers never cost a second credit
200 free credits, no card

For developers

Three endpoints for every volume

Authenticate with your API key as a Bearer token. Every response is JSON.

GET /single

Real-time checks

One address, answered in seconds. Built for sign-up forms and lead capture.

Docs

POST /batch

Small lists

Send a list in one request. Slow servers come back as processing and finish on their own.

Docs

POST /bulk

Big files

Upload a CSV, check the job's status and download the results when it finishes.

Docs

Get an API key Read the API docs

Response

What every result contains

The same fields for single and batch results. Results sit inside the payload of the response. Bulk downloads show them as readable columns such as Result, Reason and Reason code.

Field	Example	What it means
email	"[email protected]"	The address you sent.
domain	"gmial.com"	The domain part of the address.
category	"undeliverable"	deliverable, risky or undeliverable, or pending while a slow server is still being checked. Build your logic on this.
status	"possible_typo"	The reason code, such as mailbox_found, accept_all, role_address, disposable, mailbox_not_found or no_mail_server.
statusMessage	"Possible typo. Did you mean [email protected]?"	The plain reason, safe to show to people.
failType	"permanent"	permanent, temporary or none. It follows the reason code: temporary means a later check may give a different answer.
suggestion	"[email protected]"	The likely fix when we spot a typo in the domain, otherwise null.
mxLocation, siteLocation, siteLanguage	"US", "US", "en"	Where the mail servers and the website appear to be, and the site's language.

Reason codes

Every reason code maps to one category

Build your logic on category. Show statusMessage to people.

category	Reason codes in status	What to do
deliverable	mailbox_found	The mailbox exists. Safe to accept.
risky	accept_all, role_address, disposable, mailbox_unconfirmed, blocked_by_server, no_response	Catch-all, role, throwaway, or the server wouldn't confirm. Read statusMessage, then decide.
undeliverable	mailbox_not_found, mailbox_disabled, rejected, server_error, no_mail_server, invalid_format, possible_typo	Will bounce. Show the suggestion if there is one.
pending	processing	The server is slow. Ask again with GET /api-validation/single/result. Asking about that address within 30 minutes doesn't use another credit.

A pending result reads: "Still checking this mailbox. Ask again in about a minute; you will not be charged again."

Build against the sandbox first

Test API keys (sc_test_) return a fixed result for each reason code, slow checks to practise polling, simulated 429 and 500 errors, small bulk jobs and test webhooks. Nothing is really checked and no credits are used.

Sandbox docs

FAQ

API questions

Authentication, speed and limits.

Send your API key as a Bearer token in the Authorization header. Create keys in the dashboard; GET /api-validation/validate checks a key without using credits.

Still have a question? Talk to us.

An email verification API that tells you why

Three endpoints for every volume

Real-time checks

Small lists

Big files

What every result contains

Every reason code maps to one category

Build against the sandbox first

API questions

How do I authenticate?−

How fast is a single check?+

How do I handle processing?+

Batch or bulk?+

What are the rate limits?+

Is there a sandbox?+

Check your list before you send it