SMTP
Mock 450 Mailbox Unavailable Response
The requested mail action was not taken because the mailbox is temporarily unavailable. This could be due to the mailbox being locked by another process or a temporary policy restriction.
View full reference →1 HTTP Response
HTTP/1.1 450 Mailbox Unavailable
Content-Type: application/json
Date: Tue, 25 Feb 2026 12:00:00 GMT
Content-Length: 66
{
"error": "mailbox_unavailable",
"message": "Mailbox Unavailable"
}
2 Test with curl
curl -i https://httpbin.org/status/450
3 Return 450 Mailbox Unavailable in Your Framework
django
from django.http import JsonResponse
def my_view(request):
return JsonResponse(
{"error": "mailbox_unavailable", "message": "Mailbox Unavailable"},
status=450,
)
flask
from flask import Flask, jsonify
app = Flask(__name__)
@app.route("/endpoint")
def my_endpoint():
return jsonify({"error": "mailbox_unavailable", "message": "Mailbox Unavailable"}), 450
fastapi
from fastapi import FastAPI
from fastapi.responses import JSONResponse
app = FastAPI()
@app.get("/endpoint")
def my_endpoint():
return JSONResponse(
content={"error": "mailbox_unavailable", "message": "Mailbox Unavailable"},
status_code=450,
)
express.js
// Express.js
app.get('/endpoint', (req, res) => {
res.status(450).json({"error": "mailbox_unavailable", "message": "Mailbox Unavailable"});
});
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(450)
.body(Map.of("error", "mailbox_unavailable",
"message", "Mailbox Unavailable"));
}
}
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(450)
json.NewEncoder(w).Encode(map[string]string{
"error": "mailbox_unavailable",
"message": "Mailbox Unavailable",
})
}
ruby on rails
class MyController < ApplicationController
def my_action
render json: {"error": "mailbox_unavailable", "message": "Mailbox Unavailable"},
status: :mailbox_unavailable
end
end
asp.net core
// ASP.NET Core Minimal API
app.MapGet("/endpoint", () =>
Results.Json(
new { error = "mailbox_unavailable", message = "Mailbox Unavailable" },
statusCode: 450
)
);