diff --git a/api/src/main/java/be/naaturel/boardmateapi/controllers/ChatController.java b/api/src/main/java/be/naaturel/boardmateapi/controllers/ChatController.java
index 2423c9e3..f18ba839 100644
--- a/api/src/main/java/be/naaturel/boardmateapi/controllers/ChatController.java
+++ b/api/src/main/java/be/naaturel/boardmateapi/controllers/ChatController.java
@@ -17,7 +17,10 @@ import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 @RestController
 public class ChatController {
@@ -25,6 +28,7 @@ public class ChatController {
     private final MessageService messageService;
     private final WebexService webexService;
     private final MqttService mqttService;
+    private final Set<String> expectedMessages;
 
     @Autowired
     public ChatController(
@@ -34,6 +38,7 @@ public class ChatController {
         this.messageService = messageService;
         this.webexService = webexService;
         this.mqttService = mqttService;
+        this.expectedMessages = ConcurrentHashMap.newKeySet();
     }
 
     @PostMapping("/message/send")
@@ -47,11 +52,13 @@ public class ChatController {
                     messagePostRequest.getClientId(),
                     messagePostRequest.getTimeStamp());
 
-            this.webexService.post(model);
-            String id = this.messageService.save(model);
+            String messageId = this.webexService.post(model);
+            model.setId(messageId);
+            this.messageService.save(model);
+            expectedMessages.add(messageId);
 
             result.setSuccess(true);
-            result.setData(id);
+            result.setData(messageId);
             return ResponseEntity.
                     status(HttpStatus.OK)
                     .body(result);
@@ -96,27 +103,34 @@ public class ChatController {
             @RequestHeader("X-Spark-Signature") String signature,
             @RequestBody String rawPayload) {
 
-        Logger.displayInfo("========================");
         ResponseBody<Void> result = ResponseBody.createEmpty();
-
-        if (!webexService.verifySignature(rawPayload, signature)) {
-            return ResponseEntity.status(HttpStatus.FORBIDDEN).body(result);
-        }
-
         try {
+            if (!webexService.verifySignature(rawPayload, signature)) {
+                return ResponseEntity.status(HttpStatus.FORBIDDEN).body(result);
+            }
+
             ObjectMapper mapper = new ObjectMapper();
             WebexWebhook payload = mapper.readValue(rawPayload, WebexWebhook.class);
 
+            boolean accepted = expectedMessages.remove(payload.getData().getId());
+            if (accepted) {
+                Logger.displayInfo("Accepted");
+            } else {
+                Logger.displayInfo("Rejected");
+                return ResponseEntity.status(HttpStatus.UNAUTHORIZED).body(result);
+            }
+
             Room room = webexService.getRoomById(payload.getData().getRoomId());
             Message msg = webexService.fetchMessage(payload.getData().getId());
             this.messageService.save(msg);
 
             this.mqttService.publish("/chat/" + room.getClientId() + "/message", msg);
 
-            Logger.displayInfo(msg.getContent());
-            Logger.displayInfo(msg.getId());
-            Logger.displayInfo(msg.getClientId());
-            
+            Logger.displayInfo(
+                    "Webhook received : messageId=" + payload.getData().getId() +", " +
+                    "personId=" + payload.getData().getPersonId()
+            );
+
             result.setSuccess(true);
             return ResponseEntity.ok(result);
 
diff --git a/api/src/main/java/be/naaturel/boardmateapi/services/WebexService.java b/api/src/main/java/be/naaturel/boardmateapi/services/WebexService.java
index a57e2cdc..f8509c82 100644
--- a/api/src/main/java/be/naaturel/boardmateapi/services/WebexService.java
+++ b/api/src/main/java/be/naaturel/boardmateapi/services/WebexService.java
@@ -77,7 +77,7 @@ public class WebexService {
         }
     }
 
-    public void post(Message m) throws ServiceException {
+    public String post(Message m) throws ServiceException {
         try (HttpClient client = HttpClient.newHttpClient()) {
 
             Room room = getRoomByClient(m.getClientId());
@@ -91,7 +91,9 @@ public class WebexService {
                     "text", m.getContent()
             );
 
-            sendPostRequest(client, "https://webexapis.com/v1/messages", botToken, body);
+            String response = sendPostRequest(client, "https://webexapis.com/v1/messages", botToken, body);
+            JsonNode jsonNode = mapper.readTree(response);
+            return jsonNode.get("id").asText();
 
         } catch (Exception e) {
             Logger.displayError(Arrays.toString(e.getStackTrace()));