r-a-y

User registration spam is prevalent in BuddyPress.
One way to dramatically decrease signup spam is to restrict the email address domains that users can sign up with.
WordPress multisite has a native option called “Limited Email Registrations”. But this option requires you to enter the full email domain. For example, if you only wanted to allow .edu email addresses to register, this is not possible.
This plugin restricts registrations to the email domains that you are not specified in the blacklist and works in WordPress single-site and multi-site.
Plugin is a fork of r-a-y’s BP Restrict Signup by Email Domain.
Tested on BuddyPress 2.5, but should work all the way down to BuddyPress 1.6.

BP Blacklist Signup by Email Domain

Only allow users with email addresses not on the domain blacklist to register in BuddyPress.

bannersky

This plugin helps you avoid spam submissions from Gravity Forms, Formidable Forms, WPForms, Contact Form 7 and Forminator.
This is the free version and you can set it up to use a blacklist. If the field value contains / same as an item / keyword in the applied blacklist, the form submission will be blocked. It’s easy to use, you just need to create a blacklist, enable settings for the form and apply the blacklist to the form fields. You can set one or more fields to validate. Validation messages can be customized for the form.
The Pro version described here: https://www.bannersky.com/gravity-forms-blacklist-and-custom-validation/ can also be used as a whitelist, IP address, email or invitation code to validate visitor input. Support for blocking email domains, giving you the option to allow or block submissions instead of always allowing submissions. Supports blocking IP addresses by country or allowing only IP addresses from a certain country.
<h3>Short Description</h3>
This plugin helps you avoid spam submissions from Gravity Forms, Formidable Forms, WPForms, Contact Form 7 and Forminator. It checks the form field content and block submitting base on your keywords. Blocking IP, Country is only supported in the Pro version.

BSK Forms Blacklist

Perfect

Checks field content and block submitting base on your keywords. Blocking IP, Country is only supported in the Pro version.

BP Blacklist Signup by Email Domain vs BSK Forms Blacklist