wp mail content type or HTML mail template for wp_mail

https://codex.wordpress.org/Plugin_API/Filter_Reference/wp_mail_content_type

Function.php

add_filter( 'wp_mail_content_type', 'set_content_type' );
function set_content_type( $content_type ) {
 return 'text/html';
}

author based filter in all post in wp-admin in wordpress

function.php

function rudr_filter_by_the_author() { $params = array( 'name' => 'author', // this is the "name" attribute for filter <select> 'show_option_all' => 'All authors' // label for all authors (display posts without filter) );   if ( isset($_GET['user']) ) $params['selected'] = $_GET['user']; // choose selected user by $_GET variable   wp_dropdown_users( $params ); // print the ready author list }   add_action('restrict_manage_posts', 'rudr_filter_by_the_author');

https://rudrastyh.com/wordpress/filter-posts-by-author.html