SMTPing Email Verifier

SMTPing Email Verifier checks every email address when a form is submitted and rejects the ones you choose to block: mailboxes that do not exist, disposable addresses, spamtraps, blacklisted domains, known complainers and spambots. Cleaner signups mean fewer bounces, a healthier sender reputation and more accurate analytics.

Verification runs on your server through the SMTPing API. Nothing changes in your forms’ front end, and your API key is never exposed to visitors.

Two verification modes

• Full verification: syntax, DNS, a live mailbox check and every threat list in one call. One credit per new address; unknown results are never charged.
• Fast checks: spamtrap, disposable, spambot and complainer list lookups, answered in milliseconds. Ideal for high-traffic signup forms when you do not need to confirm the mailbox exists.

You decide what gets blocked

• Block by verdict: invalid, spamtrap, disposable, blacklisted, complainer, spambot, catch-all, valid catch-all, inbox full, unknown.
• Block by signal: role-based addresses (info@, sales@), free providers (for B2B-only forms), likely typos.
• Always-accept and always-block lists for addresses or whole domains. Lists are checked first and use no credit.
• Custom message shown to visitors.

Clean the addresses you already have

One click on “Analyse the site” finds the addresses your site has already collected: WordPress users (including Ultimate Member, MemberPress, Paid Memberships Pro and BuddyPress members), comment authors, WooCommerce and Easy Digital Downloads customers, MailPoet and The Newsletter Plugin subscribers, and the stored entries of Gravity Forms, WPForms Pro, Fluent Forms, Formidable, Forminator, Elementor Pro and Contact Form 7 with Flamingo. Pick the sources, duplicates are removed, and the list is verified as one job. Nothing on your site is changed.

The List tab verifies existing addresses without touching your site: paste up to 50 addresses and watch each verdict appear, or import a CSV file (read in the browser, only the addresses are sent). Filter the results by verdict and download them as CSV.

A verification widget for your visitors

Add [smtping_verify] to any page to let visitors check an address themselves. The check runs on your server, with optional per-visitor and site-wide daily limits to protect your credits. Off by default.

A log you can export

The Log tab lists every address checked by your forms and the widget, whatever the form plugin: date, address, verdict, accepted or blocked, and which form. Search, filter and export to CSV. Stored in your own database, pruned automatically (90 days by default), and covered by the WordPress personal data export and erase tools.

Built to never break your site

• Fails open: if the API is unreachable, the key is invalid or credits run out, forms keep accepting every address.
• An admin notice tells you when verification is paused and why.
• Results are cached (7 days by default) so repeat submissions do not spend credits.

32 supported plugins

Each integration switches on automatically when its plugin is detected.

WordPress core: registration (including multisite signup), comments, lost password.

Form builders: Contact Form 7, WPForms, Gravity Forms, Elementor Pro forms, Fluent Forms, Ninja Forms, Forminator, Formidable Forms, MetForm, Everest Forms, JetFormBuilder, WS Form, SureForms, Kadence Blocks forms, Bit Form, HappyForms, BuddyForms, Contact Form by BestWebSoft.

Newsletters: Mailchimp for WordPress (MC4WP), MailPoet, The Newsletter Plugin, Mail Mint. FluentCRM signup forms are built with Fluent Forms and are covered by that integration.

Membership and community: Ultimate Member, MemberPress, Paid Memberships Pro, BuddyPress.

Checkout: WooCommerce (classic checkout, block checkout, My Account registration), Easy Digital Downloads, SureCart.

Developers can register more forms through the smtping_ev_integration_classes filter, and adjust any decision with smtping_ev_should_block.

External services

This plugin connects to the SMTPing API (https://smtping.com/) to verify email addresses. It is required for the plugin to work.

No data is sent until you enter an API key. After that:

• When a visitor submits a protected form, the email address they entered is sent to https://api.smtping.com/api/v1/verify/single (full mode) or https://api.smtping.com/api/v1/checks/{check} (fast mode). Your site URL is sent in the User-Agent header.
• When you click “Test connection” in the settings, your credit balance is requested from https://api.smtping.com/api/v1/credits.
• When you use “Test an email” in the settings, the address you type is sent to the same verification endpoints.
• When a visitor uses the [smtping_verify] widget (off by default), the address they type is sent to the same verification endpoint.
• When you use “Verify the addresses already on this site”, the addresses read from your database are sent to https://api.smtping.com/api/v1/verify/bulk.
• When you verify a list in the List tab, the addresses are sent to https://api.smtping.com/api/v1/verify/single (pasted addresses) or https://api.smtping.com/api/v1/verify/bulk (CSV import).

The service is provided by SMTPing. Terms of use, Privacy policy.