area: email
action: addfolder
https://api.hypermail.com/api.php?apikey=YOURAPIKEYHERE&area=email&action=addfolder&type=lists&parent=0
<response>
<list>
<folderid>22</folderid>
<success>Folder Added</success>
</list>
</response>
{
"list": {
"folderid": "22",
"success": "Folder Added"
}
}