Gravity Forms | Create email address blacklist to send to spam

gravity-forms-send-certain-email-entries-to-spam.php

<?php
add_filter( 'gform_entry_is_spam_6', 'filter_gform_email_is_blacklist', 11, 3 );
function filter_gform_email_is_blacklist( $is_spam, $form, $entry ) {
	if ( $is_spam ) {
		return $is_spam;
	}

	$field_id = '2'; // The ID of the field containing the email address to be checked.
	$email = rgar( $entry, $field_id );

	// List of email addresses that when found in the email input value, will mark the entry as spam.
	$emails_to_block = array(
		'jon@example.com',
		'anotheruser@example.io',
		'info@acmeproducts.com',
	);
 
	if ( GFCommon::is_invalid_or_empty_email( $email ) ) {
		if ( method_exists( 'GFCommon', 'set_spam_filter' ) ) {
		GFCommon::set_spam_filter( rgar( $form, 'id' ), 'FS blacklist', 'The email was empty or invalid.' );
		}
		return true;
	}
 
	// if the email address wasn't empty and it included one of the blocked emails
	if ( ! empty( $email ) && in_array( $email, $emails_to_block ) ) {
		// log the note
		if ( method_exists( 'GFCommon', 'set_spam_filter' ) ) {
			GFCommon::set_spam_filter( rgar( $form, 'id' ), 'FS blacklist', 'The email was in our blocklist.' );
		}
		// mark it as spam
		return true;
	}

	return false;
}