Mailster Cool Captcha adds an image-based text captcha to Mailster subscription forms. Visitors type the characters shown in the image before Mailster accepts the signup, which helps reduce automated newsletter spam on your WordPress site.

Use it when you want captcha protection on Mailster forms without connecting to Google reCAPTCHA or other third-party verification services.

This plugin requires the Mailster Newsletter Plugin for WordPress 2.3 or newer. Captcha images are generated on your server (PHP GD); no external captcha API is required.

Why use Cool Captcha with Mailster?

Self-hosted captcha — Image challenges are created on your site; submissions are checked against a server-side session value.
Per-form control — Choose which Mailster subscription forms require a captcha.
Custom labels and errors — Set the field label and the message shown when verification fails.
Tune the challenge — Adjust image size, format (JPEG/PNG), quality, blur, strike-through line, word length, wave distortion, rotation, and English or Spanish word lists.
Optional skip for logged-in users — Disable the captcha for visitors who are already signed in to WordPress.
Works with GDPR fields — Field order respects Mailster GDPR checkbox placement when enabled.
Click to refresh — Subscribers can reload the captcha image if it is hard to read.

How it works

Install and activate Mailster Cool Captcha alongside Mailster.
Go to Newsletter Settings Cool Captcha.
Select the subscription forms that should show a captcha and adjust appearance options.
On submit, Mailster only accepts the signup when the entered text matches the captcha stored for that form.

Prefer Google reCAPTCHA instead? You may also try Mailster reCaptcha for Forms. Addon overview: Mailster on WordPress.org.