title: OTRS - ticket from api, can't send email notification to customer
body: <p>I'm trying to send email notification to customer after ticket is created with OTRS rest api. I know that it's impossible only with api so I created notification that reacts on TicketCreated event. My problem is email recipent. Notification is working on hardcoded email but I want to send notification to customer from ticket. When I'm selecting "customers" in recipent groups it's not working for tickets from api. But it's working for tickets created in web interface - result is that customer receive 2 emails - one original and one from notification. What I'm doing wrong? How to set customer with api? Below is my request</p>
  
  <pre><code>{
  "Ticket":{
  "Title":"REST Create Test",
  "Type":"Unclassified",
  "Queue":"Raw",
  "State":"open",
  "Priority":"3 normal",
  "CustomerUser":"customer.email@gmail.com"
  },
  "Article":{
  "Subject":"some subject ",
  "Body":"nice body",
  "ContentType":"text/plain; charset=utf8",
  "From":"otrs@fancy.company"
  }
  </code></pre>
  
  <p>}</p>