Guides & documentation
Simple explanations for everyone + technical documentation for developers.
Guides
What Is Email Validation and Why It Matters
We take a look at exactly what the email service checks and how this verification helps reduce the number of undelivered emails.
Good, Bad, Unknown: Reading Your Validation Results
We break down what each status means and what to do next with the address.
How we check if an email address exists
We examine how CleanContact verifies an address via SMTP without sending an email to the recipient.
Catch-All Domains and Why They Are Hard
Some providers accept emails sent to any address, whether it's real or not. Because of this, standard checks can sometimes be inaccurate. Here's how CleanContact determines whether an email address is valid.
Disposable emails: How we defined them
New services for creating temporary email addresses appear every day. We regularly update the list of such services to ensure they are promptly filtered out of your database.
Cut Bounce Rates and Protect Your Sender Reputation
Deliverability depends directly on your domain's reputation. Checking your mailing list before sending is the simplest and most effective step you can take to ensure your emails reach the inbox instead of ending up in the spam folder.
Delivery Rate Thresholds and Domain Blocking
We examine how the number of bounces and complaints affects email deliverability and why an email provider might restrict sending from your domain. This guide covers the thresholds, the blocking mechanism, and the sources of the underlying data.
Email normalization: standardizing addresses to a uniform format
A single address can be written in various ways. CleanContact standardizes such addresses and returns the standardized version alongside the original address.
Typo suggestions
CleanContact detects likely typos and returns the address the user most likely intended—a ready-made "did you mean?" suggestion.
Gmail Dot Trick: Catching One Mailbox Behind Many Signups
Gmail ignores dots in the local part of an address, so j.ohn@gmail.com and john@gmail.com are the same inbox; Yandex treats a dot and a hyphen as the same character. CleanContact flags when one mailbox is hiding behind several spellings on either provider.
Suspicious Addresses: Catching Spellings Real People Don't Type
Some addresses are never typed by a person at all — they are produced by a script trying to look unique on every signup. CleanContact flags a spelling that does not look human on the very first request.
Humaneness Score: A Machine-Learning Read on How Human an Address Looks
ivan.ivanov@mail.ru reads like a person. fjweowenfmewjewk@mail.ru does not. CleanContact scores that difference on a 0 to 1 scale with a machine-learning model, independent of every rule-based signal.
Documentation
API Reference: The /validate Endpoint
Everything you need to integrate: the request, the headers, the response shape, and what each status code means.
Authentication & API Keys
How keys work, where to create them, and how to keep public and server-side keys separate and safe.
Integration Examples: cURL, Node.js, Web, and PHP
Working examples of a request to the /validate endpoint in five environments: cURL, Node.js with CommonJS, Node.js with TypeScript, browser JavaScript, and PHP.
Batch Validation: Checking a Whole File of Addresses
Upload a CSV or TXT file in your account, make sure it was read correctly, start the check and download the results as a single file.