Hurray, solved my problem for main-customer:

<input name="CustomerTicketCounterToCustomer"id="CustomerTicketCounterToCustomer" type="hidden" value="1">
<input name="CustomerKey_1" id="CustomerKey_1" class="CustomerKey" type="hidden" value="mymail@mail.com">
<input class="CustomerTicketText" title="An Kundenbenutzer" name="CustomerTicketText_1"
id="CustomerTicketText_1" type="hidden" value="mymail@mail.com"
readonly="readonly" area-invalid="false">