How does Episerver recognize a cookied Marketo lead?
Episerver addes a cookie containing the lead ID when a Marketo-mapped Episerver form is submitted ad a lead is created. It will retrieve a lead based on this ID. For leads which are already in Marketo through other channels (i.e. not via an Episerver form submission), if the Marketo muchkin cookie is available in the browser and already linked to an existing lead, Episerver retrieves it though that munchkin cookie.