curl --request POST \
  --url https://yourdomain.com/send_test_email \
  --header 'Content-Type: application/json' \
  --cookie admin_cookie= \
  --data '
{
  "campaign": "test",
  "mail_data": "<string>",
  "supplied_mail_to": "<string>",
  "supplied_mail_server": "<string>",
  "supplied_smtp_from": "<string>",
  "supplied_link": "<string>",
  "supplied_id_param": "<string>",
  "target_id": "test",
  "supplied_first_name": "<string>",
  "supplied_last_name": "<string>",
  "supplied_position": "<string>",
  "supplied_custom_replacement": "<string>",
  "secure_mail": false,
  "supplied_username": "<string>",
  "supplied_password": "<string>",
  "dkim": false
}
'

"email sent"