title: Microsoft Graph WebHook: Subscription validation request timed out
body: <p>This is the ruby code I'm using to create a subscription in microsoft graph:</p>
  
  <pre><code>subscribe_endpoint = URI("https://graph.microsoft.com/v1.0/subscriptions")
  http = Net::HTTP.new(subscribe_endpoint.host, subscribe_endpoint.port)
  http.use_ssl = true
  tomorrow = Date.today + 1
  
  subscribe_request = "{
    \"changeType\": \"created,updated\",
    \"notificationUrl\": \"https://my_url/api/v1/outlook/o365notification\",
    \"resource\": \"/users/#{params[:o365account_id]}/events?$filter=Extensions/any(f:f/id eq 'Microsoft.OutlookServices.OpenTypeExtension.meeteor_event')\",
    \"expirationDateTime\": #{(Time.now + 1.day).to_json},
    \"clientState\": \"SecretClientState\"
  }"
  
  subscribe_response = http.post(
      "/v1.0/subscriptions",
      subscribe_request,
      'Authorization' =&gt; "Bearer #{params[:o365account_access_token]}",
      'Content-Type' =&gt; 'application/json'
  )
  </code></pre>
  
  <p>It worked great, but suddenly today I'm getting a <code>Subscription validation request timed out</code> response. Altough when I'm doing a POST to <code>https://my_url/api/v1/outlook/o365notification</code> it's just working fine.</p>
  
  <p>Any ideas why it stopped working when nothing changed on my side?</p>
  
  <p>Could it be that, because <code>my_url</code> points on my dev environment and is often offline, the domain got banned?</p>