Stargazer

<h4>An easy and effective solution against Comment Spam</h4>
<p>WP-BlackCheck combines various ideas to protect your blog from spam.</p>
<h4>Fearures</h4>
<ul>
<li>Easy Installation</li>
<li>Block known spammers</li>
<li>Block Trackback/Pingback spam</li>
<li>No need to adjust default templates</li>
<li>Spam counter on the dashboard</li>
<li>Statistics</li>
</ul>
<h4>Languages</h4>
<ul>
<li>Albanian (thanks to Taulant Ceka – http://sem.al )</li>
<li>English</li>
<li>German</li>
<li>Slovakian (thanks to Black Cat Artworks – http://blackcatartworks.eu/ )</li>
</ul>
<p>If you want to see this plugin in your language, feel free to contact me or use <a href="https://www.transifex.net/projects/p/wpbc/resource/plugin/" rel="nofollow ugc">transifex.net</a> to contribute.</p>
<h4>Links</h4>
<ul>
<li><a href="http://my.stargazer.at/" title="Authors blog" rel="nofollow ugc">Blog</a></li>
<li><a href="http://bugs.stargazer.at/" title="Bugtracker" rel="nofollow ugc">Bugtracker</a></li>
<li><a href="http://www.twitter.com/ToeiRei" rel="nofollow ugc">Twitter</a></li>
</ul>
<h4>History</h4>
<p>Blocking spammers via htaccess or other server settings would do the job, but that would require<br />
to keep all the files in sync. So I decided to write a centralized solution that enables<br />
innocent users to remove their IP from the blacklist via removal request. As a blacklist gets queried<br />
way too often, I added some local detection of spammers to reduce load at my side.<br />
By now many additional features have been added, making this plugin a full grown anti-spam solution.</p>


WP-BlackCheck

WP-BlackCheck is an Anti-Spam Solution for Wordpress blocking spam using local detection and a centralized Blacklist Service.

CreativeMindsSolutions

<p><a href="https://www.cminds.com/wordpress-plugins-library/email-registration-blacklist-plugin-for-wordpress/" rel="nofollow ugc">Pro Plugin Page</a> | <a href="https://www.videolessonsplugin.com/video-lesson/lesson/email-domain-blacklist-plugin/" rel="nofollow ugc">Videos</a> | <a href="https://creativeminds.helpscoutdocs.com/category/285-email-registration-blacklist-cmrb" rel="nofollow ugc">User Guide</a></p>
<p><strong>Safeguard your WordPress site from unauthorized registrations and spammers by implementing personalized rules for blacklisting and whitelisting with our WordPress blacklist plugin solution.</strong></p>
<p>This plugin allows you to block or allow users to enter your website based on specific criteria. With customizable domain, IP and email blacklists you can prevent users from registering.</p>
<p>Conversely, thanks to the whitelist feature of our WordPress plugin, you can ensure that only users with approved email domains, usernames, or IP addresses can register.</p>
<h3>Enhance WordPress Site Security</h3>
<p>Our blacklist plugin enables you to increase the security of your WordPress site and prevent spam registrations from fake or malicious users.</p>
<p>Additionally, this feature-packed tool gives you greater control over who can access your site’s and community content.</p>
<h3>Email Blacklist and Anti-Spam plugin Premium Editions</h3>
<p>The <a href="https://www.cminds.com/wordpress-plugins-library/email-registration-blacklist-plugin-for-wordpress/" rel="nofollow ugc">Email Blacklist and Anti-Spam Plugin Premium editions</a> includes even more powerful features, such as: support for contact forms and WordPress comments, white list and blacklist features work across domains and emails, domain and email testing tool and much more.</p>
<h3>Email Blacklist and Anti-Spam plugin Introduction Video</h3>
<div class="embed-vimeo" style="text-align: center;"><iframe loading="lazy" src="https://player.vimeo.com/video/123027044" width="750" height="422" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe></div>
<h3>How to Use the Email Blacklist Feature of the Plugin</h3>
<ul>
<li><strong>Closed Beta</strong> – Control users in your beta site release.</li>
<li><strong>Members Only</strong> – Add suspicious domains to the blacklist and block their users from registrating.</li>
<li><strong>Spam blocker</strong> – Prevent spam users from registering.</li>
</ul>
<h3>Basic WordPress Blacklist Plugin Features</h3>
<ul>
<li>Support Free Domain List from SpamAssassin.</li>
<li>Support a domain whitelist plugin feature.</li>
<li>Support an email blacklist plugin feature.</li>
<li>Support an IP whitelist plugin feature.</li>
<li>Admin can edit front-end labels and messages.</li>
<li>Includes tester.</li>
</ul>
<h3>Pro Version</h3>
<p><a href="https://www.cminds.com/wordpress-plugins-library/email-registration-blacklist-plugin-for-wordpress/" rel="nofollow ugc">Pro Version Detailed Features List</a></p>
<ul>
<li>Support DNSBL online service.</li>
<li>Support domain blacklist and whitelist features.</li>
<li>Support email blacklist and whitelist features.</li>
<li>Support IP blacklist and whitelist features.</li>
<li>Control who is allowed to comment.</li>
<li>Access to failed registration log.</li>
<li>Additional errors messages to show to users trying to register.</li>
<li>Edit profile restriction.</li>
<li>Support importing list of emails from CSV.</li>
<li>Includes domain & email tester.</li>
<li>Special Gmail support.</li>
<li>Special characters support.</li>
<li>Contact Form 7 integration.</li>
<li>ChatGPT integration.</li>
</ul>
<h3>Follow Us</h3>
<p><a href="https://www.cminds.com/category/wordpress/" rel="nofollow ugc">Blog</a> | <a href="http://twitter.com/cmplugins" rel="nofollow ugc">Twitter</a> | <a href="https://www.linkedin.com/company/creativeminds" rel="nofollow ugc">LinkedIn</a> | <a href="https://www.youtube.com/user/cmindschannel" rel="nofollow ugc">YouTube</a> | <a href="http://www.pinterest.com/cmplugins/" rel="nofollow ugc">Pinterest</a> | <a href="https://www.facebook.com/cmplugins/" rel="nofollow ugc">Facebook</a></p>
<h3>Suggested Plugins by CreativeMinds</h3>
<p>List of all <a href="https://www.cminds.com" rel="nofollow ugc">WordPress Plugins</a> by CreativeMinds</p>
<ul>
<li><a href="https://glossaryplugin.com/" rel="nofollow ugc">CM Tooltip Glossary</a> – Easily creates a Glossary, Encyclopaedia or Dictionary of your website’s terms and shows them as a tooltip in posts and pages when hovering. With many more powerful features.</li>
<li><a href="https://www.downloadmanagerplugin.com/" rel="nofollow ugc">CM Download Manager</a> – Allows users to upload, manage, track and support documents or files in a download directory listing database for others to contribute, use and comment upon.</li>
<li><a href="https://www.answersplugin.com/" rel="nofollow ugc">CM Answers Plugin</a> – A fully-featured WordPress Questions & Answers Plugin that allows you to build multiple discussion forum systems Just like StackOverflow, Yahoo Answers and Quora, Now with MicroPayments and Anonymous posting support.</li>
<li><a href="http://restrictcontent.com/" rel="nofollow ugc">CM Restrict Content</a> – A full-featured, powerful membership solution and content restriction plugin for WordPress. Support access by role to content on your site.</li>
<li><a href="http://bookingcalendarplugin.com/" rel="nofollow ugc">CM Booking Calendar</a> – Customers can easily schedule appointments and pay for them directly through your website.</li>
</ul>


CM E-Mail Blacklist – Simple email filtering for safer registration

The most people are using free emails like aol gmail freenet gmx and so, why to forbid them. And spammer users are using m.niepytajnic1.info.pl
weihnachts-gruesse.info
cbdolejki.pl 

or so. There is no blacklist for them.

I really don't understand the sinn of this plugin

Useless

Block unwanted email registrations on your site with this email blacklist plugin. Protect your site by preventing spam sign-ups.

WP-BlackCheck vs CM E-Mail Blacklist – Simple email filtering for safer registration