SOLVED: Blocking registrations from a specific email domain

As a follow up to Blocking registrations from a specific email domain (closed to replies) I wanted to share a solution I made for this that uses a filter from the core registration process (registration_errors).

This filter can be used to just block the registrations (does not require WordFence in that case):

add_filter( 'registration_errors', 'disable_user_registration_for_email_domain', 10, 3 );
function disable_user_registration_for_email_domain ( $errors, $sanitized_user_login, $user_email ) {
	// only if it's an email address at all 
	if ( ! is_email( $user_email ) ) {
		return $errors;
	}

	// get domain from email address
	$email_domain = substr( $user_email, strrpos( $user_email, '@' ) + 1 );
	$block_domains = [ // partial domain names allowed (doesn't need to include TLD for example)
		'spammersgalore.com',
	];

	foreach ( $block_domains as $domain_partial ) {
		if ( stripos( $email_domain, $domain_partial ) !== false ) {
			// throw registration error
			$errors->add( 'email_error', '<strong>ERROR</strong>: Registration not allowed.' );
		}
	}

	return $errors;
}

Or including the wordfence function to temporarily lock out the IP that was attempting the registration entirely:

add_filter( 'registration_errors', 'disable_user_registration_for_email_domain', 10, 3 );
function disable_user_registration_for_email_domain ( $errors, $sanitized_user_login, $user_email ) {
	// only execute when the relevant WordFence functions can be called
	if ( ! is_callable( 'wfUtils', 'getIP' ) || ! is_callable( 'wfBlock', 'isWhitelisted' ) || ! is_callable( 'wordfence', 'lockOutIP' )) {
		return $errors;
	}

	// only if it's an email address at all 
	if ( ! is_email( $user_email ) ) {
		return $errors;
	}

	// get domain from email address
	$email_domain = substr( $user_email, strrpos( $user_email, '@' ) + 1 );
	$block_domains = [ // partial domain names allowed (doesn't need to include TLD for example)
		'spammersgalore.com',
	];

	foreach ( $block_domains as $domain_partial ) {
		if ( stripos( $email_domain, $domain_partial ) !== false ) {
			$IP = \wfUtils::getIP();
			if ( \wfBlock::isWhitelisted( $IP ) ) {
				return $errors; // don't block whitelisted IPs
			}
			// lockout IP
			\wordfence::lockOutIP( $IP, "Registration attempt from blocked email domain {$domain_partial}" );
			// throw registration error
			$errors->add( 'email_error', '<strong>ERROR</strong>: Registration not allowed.' );
		}
	}

	return $errors;
}

I hope this will be useful to someone. Tagging @ps6818 @nigelhay @jcpacelli @sidbicious @mouriana @dougrees from the previous topic in case they’re still interested in this

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