Apply suggestion from @notamitgamer

domains/send.eunsunglee.json

@@ -1,7 +1,7 @@
 {
   "owner": { "username": "eunsunglee0524" },
   "records": {
-    "MX": [{ "priority": 10, "value": "feedback-smtp.ap-northeast-1.amazonses.com" }],
+    "MX": [{ "priority": 10, "target": "feedback-smtp.ap-northeast-1.amazonses.com" }],
     "TXT": ["v=spf1 include:amazonses.com ~all"]
   }
 }