Domain mapping list copied from phplistplugin
See original file at https://github.com/michield/phplist-plugin-domainthrottlemap/blob/master/plugins/domainthrottlemap.php
Original author: Michiel Dethmers
See original file at https://github.com/michield/phplist-plugin-domainthrottlemap/blob/master/plugins/domainthrottlemap.php
Original author: Michiel Dethmers