Active installations10Adoption metric — not a quality score
WordPress.org ratingNo WordPress.org ratings yet
Official packageDirect from WordPress.org
Repository metrics are context, not quality scores. Active installations measure adoption and can strongly reflect a plugin’s age and historical popularity. Ratings, recent updates and “Tested up to” metadata also do not guarantee modern code, error-free operation, security, feature completeness or suitability for a particular site. Why active installs don’t tell the whole story →
WP PlugIndex currently records Mailster Kickbox version 1.2.1 as active, updated 19d ago and tested up to WordPress 7.1.
Overview
About this plugin
Mailster Kickbox adds real-time Kickbox email verification and email validation to the Mailster Newsletter Plugin for WordPress. When someone subscribes, the address is checked through the Kickbox API before it is saved—so invalid, disposable, and low-quality emails stay out of your list.
Cleaner lists mean fewer hard bounces, stronger sender reputation, and better email deliverability for your Mailster campaigns.
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0 or newer and a Kickbox account with an API key. Subscriber email addresses are sent to Kickbox for verification.
Why use Kickbox email verification with Mailster?
Real-time verification on signup — Kickbox validates the address as soon as someone subscribes through Mailster (forms, admin, and other flows that use Mailster’s subscriber verification).
Fewer bounces — Undeliverable and rejected addresses are blocked before they hurt your reputation.
Sendex quality score — Set a minimum Kickbox Sendex threshold so only higher-quality addresses are accepted.
Rules you control — Accept or reject based on Kickbox results ( deliverable, risky, unknown, undeliverable ) and detailed reason codes.
Custom error messages — Show clear feedback when an email is not accepted.
Configurable timeout — Adjust how long Kickbox may take to respond (milliseconds).
Credit balance in settings — See remaining Kickbox verification credits from the Mailster settings screen.
Optional import checks — Enable verification during bulk import, or keep imports fast and verify large lists in Kickbox first.
How it works
Install and activate Mailster Kickbox alongside Mailster.
Enter your Kickbox API key under Newsletter → Settings → Kickbox.
Adjust acceptance rules if you need stricter or looser filtering.
New subscribers are verified automatically via the Kickbox Verify API.
Learn more about verification results in the Kickbox API documentation and result terminology. Addon overview: Use Kickbox with Mailster.
Additional Info
0 or newer and an account at Kickbox. Subscriber emails are verified via the Kickbox API.
WordPress.org metadata
Plugin tags
Topics listed for this plugin in the WordPress.org directory.
email validation
email verification
deliverability
kickbox
mailster
Compatibility & maintenance
Compatibility & maintenance
Tested with WP 7.1
Marked as tested with the current WordPress 7.1 release.
Current WordPress releaseWordPress 7.1
WordPress.org Tested up to7.1
Minimum requirementsWordPress 6.0 · PHP not listed
Update activity13 Oct 202619d ago
“Tested up to” is directory metadata supplied by the plugin author. WP PlugIndex does not turn an older declaration into a claim that the plugin is incompatible.
Changes recorded by WP PlugIndex
Recent tracked changes
Version1.2.0→1.2.1
WordPress compatibility6.5.10→7.1.3
Tracking & source
WP PlugIndex tracks public WordPress.org directory metadata and records selected version, compatibility and availability changes as they are detected.
