I know that I can't guarantee emails are valid without signups, but I noticed a problematic user wanting to troll was using @example.com email addresses.

How might I maintain a blacklist of such domains for comment authors? Specifically, how might I reject comments immediately if such a domain is used, notifying the user as such?

A wp_die('you must use a real email'); will likely do the trick, but which filter/when should the check be made?


Here's a suggestion for a filter:

 * Filters a comment's approval status before it is set.
 * @since 2.1.0
 * @since 4.9.0 Returning a WP_Error value from the filter will shortcircuit comment insertion and
 *              allow skipping further processing.
 * @param bool|string|WP_Error $approved    The approval status. Accepts 1, 0, 'spam' or WP_Error.
 * @param array                $commentdata Comment data.
$approved = apply_filters( 'pre_comment_approved', $approved, $commentdata );

where we can e.g. try the email domain parser by Gabriel Livan:

add_filter( 'pre_comment_approved', function( $approved, $commentdata ) {
    $domain = substr( strrchr( $commentdata['comment_author_email'], '@' ), 1 );
    $banned_domains = [
    if ( in_array( $domain, $banned_domains ) ) {
        wp_die( __( 'Please use a real email!' ) );
        //return new WP_Error( 'comment_real_email', __( 'Please use a real email!' ) );
    return $approved;
}, 10, 2 );

where $banned_domains is the list of email domains we want to stop before it's saved into our database.

Another one that fires earlier is:

 * Filters a comment's data before it is sanitized and inserted into the database.
 * @since 1.5.0
 * @param array $commentdata Comment data.
$commentdata = apply_filters( 'preprocess_comment', $commentdata );
| improve this answer | |
  • So this almost works, and results in a blank screen if i add in the email via commentdata – Tom J Nowell Apr 24 '18 at 13:22
  • Updated with a slightly modified version of the code with a blacklist, and swapped the return for a wp_die statement – Tom J Nowell Apr 24 '18 at 13:28

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