SMTP
Mock 221 Closing Connection Response
The server is closing the transmission channel. This is the normal response to the QUIT command, indicating a graceful end to the SMTP session.
View full reference →1 HTTP Response
HTTP/1.1 221 Closing Connection
Content-Type: application/json
Date: Tue, 25 Feb 2026 12:00:00 GMT
Content-Length: 21
{
"status": "success"
}
2 Test with curl
curl -i https://httpbin.org/status/221
3 Return 221 Closing Connection in Your Framework
django
from django.http import JsonResponse
def my_view(request):
return JsonResponse(
{"status": "success"},
status=221,
)
flask
from flask import Flask, jsonify
app = Flask(__name__)
@app.route("/endpoint")
def my_endpoint():
return jsonify({"status": "success"}), 221
fastapi
from fastapi import FastAPI
from fastapi.responses import JSONResponse
app = FastAPI()
@app.get("/endpoint")
def my_endpoint():
return JSONResponse(
content={"status": "success"},
status_code=221,
)
express.js
// Express.js
app.get('/endpoint', (req, res) => {
res.status(221).json({"status": "success"});
});
spring boot
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import java.util.Map;
@RestController
public class MyController {
@GetMapping("/endpoint")
public ResponseEntity<Map<String, Object>> myEndpoint() {
return ResponseEntity
.status(221)
.body(Map.of("error", "closing_connection",
"message", "Closing Connection"));
}
}
go net/http
package main
import (
"encoding/json"
"net/http"
)
func myHandler(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(221)
json.NewEncoder(w).Encode(map[string]string{
"error": "closing_connection",
"message": "Closing Connection",
})
}
ruby on rails
class MyController < ApplicationController
def my_action
render json: {"status": "success"},
status: :closing_connection
end
end
asp.net core
// ASP.NET Core Minimal API
app.MapGet("/endpoint", () =>
Results.Json(
new { error = "closing_connection", message = "Closing Connection" },
statusCode: 221
)
);