Hi, Brajesh.

Thanks for replying.

But the code is not sending email to the user followers when the user publishes a post, here is a complete code.

function wpdocs_set_html_mail_content_type() {
    return 'text/html';
}
function post_notification($post_ID) {
    global $wpdb ;

    $post = get_post($post_ID) ;
    add_filter( 'wp_mail_content_type', 'wpdocs_set_html_mail_content_type' );

    $aUsersID = bp_get_following_ids('user_id='.bp_loggedin_user_id() );
    foreach($aUsersID as $iUserID) {
        $user     = get_userdata($iUserID) ;
        
        $to       = $user->user_email ;
        $subject  = '[' . get_bloginfo('name') . '] Nuevo post en el blog' ;
        $message  = 'Nuevo Post: <a href="' . get_permalink($post_ID) . '">' . $post->post_title . '</a>' ;
        $message .= '<br/><br/>' ;
        $message .= nl2br($post->post_content) ;
        wp_mail( $to, $subject, $message ) ;
    }
}

add_action('publish_post', 'post_notification') ;

Thanks Ravi , it is working fine.

I am using buddypress legacy template.