curl --request PATCH \
  --url https://api.lemlist.com/api/campaigns/{campaignId}/leads/{leadId} \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "preferredContactMethod": "email"
}
'

{
  "campaignId": "cam_bSn8EORHQxbWPjHvu",
  "campaignName": "NEW TO DELETE",
  "leadUrl": "https://api.lemlist.com/api/leads/alex.doe%40example.com",
  "firstName": "John",
  "lastName": "Doe",
  "companyName": "Acme Inc",
  "jobTitle": "Growth Engineer",
  "companyDomain": "example.com",
  "email": "support@lemlist.com",
  "preferredContactMethod": "email",
  "_id": "lea_fiDpiGV585wy3Oii2",
  "isPaused": false,
  "contactId": "ctc_xW8Ou6C03Csv8vatp",
  "emailStatus": "deliverable"
}