> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.freecustom.email/free-custom-email-api/v-1/inboxes/register-an-inbox/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.freecustom.email/_mcp/server.

# Register an inbox

POST https://api2.freecustom.email/v1/inboxes
Content-Type: application/json

Registers an inbox for API use.

**Platform domain inbox:** The domain must appear in `GET /v1/domains` for your plan.

**Custom domain inbox:** The domain must be added and verified via
`POST /v1/custom-domains` + `POST /v1/custom-domains/{domain}/verify`
before registering inboxes at it. Requires Growth+ plan.

Reference: https://docs.freecustom.email/free-custom-email-api/v-1/inboxes/register-an-inbox

## Authentication

- `Authorization` header (bearer token, required) — Bearer authentication of the form `Bearer <token>`, where token is your auth token.

## Request

### Body (application/json)

This endpoint expects an object.

- `inbox` (string, required)

## Response

### 200

OK

- `success` (boolean, required)
- `message` (string, required)
- `inbox` (string, required)

### 201

Created

- `success` (boolean, required)
- `data` (V1InboxesPostResponsesContentApplicationJsonSchemaData, required)

## Errors

### 400 Bad Request Error

Bad Request

- `success` (boolean, required)
- `error` (string, required)
- `message` (string, required)

### 401 Unauthorized Error

Unauthorized

- `success` (boolean, required)
- `error` (string, required)
- `message` (string, required)

### 403 Forbidden Error

Forbidden

- `success` (boolean, required)
- `error` (string, required)
- `message` (string, required)
- `upgrade_url` (string, required)

### 429 Too Many Requests Error

Too Many Requests

- `success` (boolean, required)
- `error` (string, required)
- `message` (string, required)
- `upgrade_url` (string, required)
- `credits_url` (string, required)
- `hint` (string, required)

## Types

### V1InboxesPostResponsesContentApplicationJsonSchemaData

- `inbox` (string, required)
- `registered_at` (datetime, required)

## Examples

### v1_inboxes_Register an inbox_example

**Request**

```json
{
  "inbox": "test@ditube.info"
}
```

**Response**

```json
{
  "success": true,
  "message": "Inbox already registered.",
  "inbox": "string"
}
```

**SDK Code**

```python v1_inboxes_Register an inbox_example
import requests

url = "https://api2.freecustom.email/v1/inboxes"

payload = { "inbox": "test@ditube.info" }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.json())
```

```javascript v1_inboxes_Register an inbox_example
const url = 'https://api2.freecustom.email/v1/inboxes';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{"inbox":"test@ditube.info"}'
};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}
```

```go v1_inboxes_Register an inbox_example
package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api2.freecustom.email/v1/inboxes"

	payload := strings.NewReader("{\n  \"inbox\": \"test@ditube.info\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(res)
	fmt.Println(string(body))

}
```

```ruby v1_inboxes_Register an inbox_example
require 'uri'
require 'net/http'

url = URI("https://api2.freecustom.email/v1/inboxes")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"inbox\": \"test@ditube.info\"\n}"

response = http.request(request)
puts response.read_body
```

```java v1_inboxes_Register an inbox_example
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://api2.freecustom.email/v1/inboxes")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"inbox\": \"test@ditube.info\"\n}")
  .asString();
```

```php v1_inboxes_Register an inbox_example
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api2.freecustom.email/v1/inboxes', [
  'body' => '{
  "inbox": "test@ditube.info"
}',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);

echo $response->getBody();
```

```csharp v1_inboxes_Register an inbox_example
using RestSharp;

var client = new RestClient("https://api2.freecustom.email/v1/inboxes");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{\n  \"inbox\": \"test@ditube.info\"\n}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift v1_inboxes_Register an inbox_example
import Foundation

let headers = [
  "Authorization": "Bearer <token>",
  "Content-Type": "application/json"
]
let parameters = ["inbox": "test@ditube.info"] as [String : Any]

let postData = JSONSerialization.data(withJSONObject: parameters, options: [])

let request = NSMutableURLRequest(url: NSURL(string: "https://api2.freecustom.email/v1/inboxes")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers
request.httpBody = postData as Data

let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
  if (error != nil) {
    print(error as Any)
  } else {
    let httpResponse = response as? HTTPURLResponse
    print(httpResponse)
  }
})

dataTask.resume()
```

### v1_inboxes_Register an inbox_example

**Request**

```json
{
  "inbox": "test@ditube.info"
}
```

**Response**

```json
{
  "success": true,
  "data": {
    "inbox": "string",
    "registered_at": "2020-09-26T09:23:12.501Z"
  }
}
```

**SDK Code**

```python v1_inboxes_Register an inbox_example
import requests

url = "https://api2.freecustom.email/v1/inboxes"

payload = { "inbox": "test@ditube.info" }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.json())
```

```javascript v1_inboxes_Register an inbox_example
const url = 'https://api2.freecustom.email/v1/inboxes';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{"inbox":"test@ditube.info"}'
};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}
```

```go v1_inboxes_Register an inbox_example
package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api2.freecustom.email/v1/inboxes"

	payload := strings.NewReader("{\n  \"inbox\": \"test@ditube.info\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(res)
	fmt.Println(string(body))

}
```

```ruby v1_inboxes_Register an inbox_example
require 'uri'
require 'net/http'

url = URI("https://api2.freecustom.email/v1/inboxes")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"inbox\": \"test@ditube.info\"\n}"

response = http.request(request)
puts response.read_body
```

```java v1_inboxes_Register an inbox_example
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://api2.freecustom.email/v1/inboxes")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"inbox\": \"test@ditube.info\"\n}")
  .asString();
```

```php v1_inboxes_Register an inbox_example
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api2.freecustom.email/v1/inboxes', [
  'body' => '{
  "inbox": "test@ditube.info"
}',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);

echo $response->getBody();
```

```csharp v1_inboxes_Register an inbox_example
using RestSharp;

var client = new RestClient("https://api2.freecustom.email/v1/inboxes");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{\n  \"inbox\": \"test@ditube.info\"\n}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift v1_inboxes_Register an inbox_example
import Foundation

let headers = [
  "Authorization": "Bearer <token>",
  "Content-Type": "application/json"
]
let parameters = ["inbox": "test@ditube.info"] as [String : Any]

let postData = JSONSerialization.data(withJSONObject: parameters, options: [])

let request = NSMutableURLRequest(url: NSURL(string: "https://api2.freecustom.email/v1/inboxes")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers
request.httpBody = postData as Data

let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
  if (error != nil) {
    print(error as Any)
  } else {
    let httpResponse = response as? HTTPURLResponse
    print(httpResponse)
  }
})

dataTask.resume()
```