Create Incident using Email as LookUp

Content

I am trying to create an incident from an external system. I only want to make 1 API call. How can I do it without looking up a contact, just sending an email address. I know that the email may match more then 1 contact, and I am not picky about which contact it get associated with, I prefer the most recent, but again, not critical.

Version

18A

Code Snippet

{
"primaryContact":
    {
    "lookupName": "[email protected]"
    },
"subject": "New Incident",
"category": {
        "id": 3433
        },
"disposition": {
        "id": 3642
        },        
"product": {
        "id": 3602
        },
"assignedTo": {
        "staffGroup":{
            "id": 106101
            }
        },
"queue": {
    "id": 47
}
}