你会陷入profile_update 和user_register. 首先检查是否是新用户，以及她是否是管理员/编辑。

然后发送邮件。更新用户的情况也一样：查看角色是否已更改，以及新角色是admin还是editor。

<?php
add_action( \'profile_update\', \'wpse33949_profile_update\' );
add_action( \'user_register\', \'wpse33949_profile_update\' );
function wpse33949_profile_update( $user_id, $old_user_data = false )
{
    // get the updated user data
    $userdata = get_userdata( $user_id );

    // whatever you need to send here
    $message = "Sign up for my email!";
    $subject = "Mailing List";

    if( ! $old_user_data && in_array( $userdata->user_role, array( \'editor\', \'administrator\' ) ) )
    {
        // we\'re inserting a new user...
        wp_mail( $userdata->user_email, $subject, $message );
    }
    elseif( in_array( $userdata->user_role, array( \'editor\', \'administrator\' ) ) && $userdata->user_role != $old_user_data->user_role )
    {
        // We\'re updating the role of an existing user, make sure they\'re 
        // becoming an admin or editor, then send the message.
        wp_mail( $userdata->user_email, $subject, $message );
    }
}