<https://www.combell.com/en/help/kb/where-can-i-find-the-mail-headers-in-thunderbird/#breadcrumb>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.combell.com/en/help/kb/where-can-i-find-the-mail-headers-in-thunderbird/>