I have found a nested subscribe function is easier to use than the write collection function Because you can create the recipient record and subscribe them to a service in one shot.
var service = "serv1_internalName";
var create = true;
for (a in emails.Results) {
rcp += "<recipient _key='@email' email='" + emails.Results[a].EmailAddress +"' firstName='Testing2'/>";
nms.subscription.Subscribe(service, rcp, create)
};