# Add a custom domain

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

Adds a new custom domain to your account and returns the DNS records
you must configure at your registrar before verifying.

**Plan required:** Growth ($49/mo) or Enterprise ($149/mo).

**Workflow:**
1. `POST /v1/custom-domains` — add the domain, get DNS records.
2. Add the two DNS records (MX + TXT) at your registrar.
3. `POST /v1/custom-domains/{domain}/verify` — confirm propagation.
4. `POST /v1/inboxes` with any address `@yourdomain` — start receiving mail.

This call is **idempotent** — if the domain is already added it returns
the existing entry with `200` instead of `201`.

**Limits:** Maximum 10 custom domains per account.


Reference: https://docs.freecustom.email/free-custom-email-api/v-1/custom-domains/add-a-custom-domain

## OpenAPI Specification

```yaml
openapi: 3.1.0
info:
  title: collection
  version: 1.0.0
paths:
  /v1/custom-domains:
    post:
      operationId: add-a-custom-domain
      summary: Add a custom domain
      description: >
        Adds a new custom domain to your account and returns the DNS records

        you must configure at your registrar before verifying.


        **Plan required:** Growth ($49/mo) or Enterprise ($149/mo).


        **Workflow:**

        1. `POST /v1/custom-domains` — add the domain, get DNS records.

        2. Add the two DNS records (MX + TXT) at your registrar.

        3. `POST /v1/custom-domains/{domain}/verify` — confirm propagation.

        4. `POST /v1/inboxes` with any address `@yourdomain` — start receiving
        mail.


        This call is **idempotent** — if the domain is already added it returns

        the existing entry with `200` instead of `201`.


        **Limits:** Maximum 10 custom domains per account.
      tags:
        - subpackage_v1.subpackage_v1/customDomains
      parameters:
        - name: Authorization
          in: header
          description: Bearer authentication
          required: true
          schema:
            type: string
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: >-
                  #/components/schemas/v1_custom-domains_Add a custom
                  domain_Response_200
        '400':
          description: Bad Request
          content:
            application/json:
              schema:
                $ref: >-
                  #/components/schemas/PostV1Custom-domainsRequestBadRequestError
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                $ref: >-
                  #/components/schemas/PostV1Custom-domainsRequestUnauthorizedError
        '403':
          description: Forbidden
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/PostV1Custom-domainsRequestForbiddenError'
        '429':
          description: Too Many Requests
          content:
            application/json:
              schema:
                $ref: >-
                  #/components/schemas/PostV1Custom-domainsRequestTooManyRequestsError
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                domain:
                  type: string
              required:
                - domain
servers:
  - url: https://api2.freecustom.email
components:
  schemas:
    V1CustomDomainsPostResponsesContentApplicationJsonSchemaDataDnsRecordsItems:
      type: object
      properties:
        ttl:
          type: string
        type:
          type: string
        value:
          type: string
        hostname:
          type: string
        priority:
          type: string
      required:
        - ttl
        - type
        - value
        - hostname
        - priority
      title: >-
        V1CustomDomainsPostResponsesContentApplicationJsonSchemaDataDnsRecordsItems
    V1CustomDomainsPostResponsesContentApplicationJsonSchemaData:
      type: object
      properties:
        domain:
          type: string
        added_at:
          type: string
          format: date-time
        verified:
          type: boolean
        mx_record:
          type: string
        next_step:
          type: string
        txt_record:
          type: string
        dns_records:
          type: array
          items:
            $ref: >-
              #/components/schemas/V1CustomDomainsPostResponsesContentApplicationJsonSchemaDataDnsRecordsItems
      required:
        - domain
        - added_at
        - verified
        - mx_record
        - next_step
        - txt_record
        - dns_records
      title: V1CustomDomainsPostResponsesContentApplicationJsonSchemaData
    v1_custom-domains_Add a custom domain_Response_200:
      type: object
      properties:
        data:
          $ref: >-
            #/components/schemas/V1CustomDomainsPostResponsesContentApplicationJsonSchemaData
        message:
          type: string
        success:
          type: boolean
      required:
        - data
        - message
        - success
      title: v1_custom-domains_Add a custom domain_Response_200
    PostV1Custom-domainsRequestBadRequestError:
      type: object
      properties:
        error:
          type: string
        message:
          type: string
        success:
          type: boolean
      required:
        - error
        - message
        - success
      title: PostV1Custom-domainsRequestBadRequestError
    PostV1Custom-domainsRequestUnauthorizedError:
      type: object
      properties:
        error:
          type: string
        message:
          type: string
        success:
          type: boolean
      required:
        - error
        - message
        - success
      title: PostV1Custom-domainsRequestUnauthorizedError
    PostV1Custom-domainsRequestForbiddenError:
      type: object
      properties:
        error:
          type: string
        message:
          type: string
        success:
          type: boolean
        upgrade_url:
          type: string
          format: uri
      required:
        - error
        - message
        - success
        - upgrade_url
      title: PostV1Custom-domainsRequestForbiddenError
    PostV1Custom-domainsRequestTooManyRequestsError:
      type: object
      properties:
        hint:
          type: string
        error:
          type: string
        message:
          type: string
        success:
          type: boolean
        credits_url:
          type: string
          format: uri
        upgrade_url:
          type: string
          format: uri
      required:
        - hint
        - error
        - message
        - success
        - credits_url
        - upgrade_url
      title: PostV1Custom-domainsRequestTooManyRequestsError
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer

```

## SDK Code Examples

```python v1_custom-domains_Add a custom domain_example
import requests

url = "https://api2.freecustom.email/v1/custom-domains"

payload = { "domain": "mail.acme.com" }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.json())
```

```javascript v1_custom-domains_Add a custom domain_example
const url = 'https://api2.freecustom.email/v1/custom-domains';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{"domain":"mail.acme.com"}'
};

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

```go v1_custom-domains_Add a custom domain_example
package main

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

func main() {

	url := "https://api2.freecustom.email/v1/custom-domains"

	payload := strings.NewReader("{\n  \"domain\": \"mail.acme.com\"\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_custom-domains_Add a custom domain_example
require 'uri'
require 'net/http'

url = URI("https://api2.freecustom.email/v1/custom-domains")

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  \"domain\": \"mail.acme.com\"\n}"

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

```java v1_custom-domains_Add a custom domain_example
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://api2.freecustom.email/v1/custom-domains")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"domain\": \"mail.acme.com\"\n}")
  .asString();
```

```php v1_custom-domains_Add a custom domain_example
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api2.freecustom.email/v1/custom-domains', [
  'body' => '{
  "domain": "mail.acme.com"
}',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);

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

```csharp v1_custom-domains_Add a custom domain_example
using RestSharp;

var client = new RestClient("https://api2.freecustom.email/v1/custom-domains");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{\n  \"domain\": \"mail.acme.com\"\n}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift v1_custom-domains_Add a custom domain_example
import Foundation

let headers = [
  "Authorization": "Bearer <token>",
  "Content-Type": "application/json"
]
let parameters = ["domain": "mail.acme.com"] as [String : Any]

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

let request = NSMutableURLRequest(url: NSURL(string: "https://api2.freecustom.email/v1/custom-domains")! 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()
```

```python v1_custom-domains_Add a custom domain_example
import requests

url = "https://api2.freecustom.email/v1/custom-domains"

payload = { "domain": "mail.acme.com" }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.json())
```

```javascript v1_custom-domains_Add a custom domain_example
const url = 'https://api2.freecustom.email/v1/custom-domains';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{"domain":"mail.acme.com"}'
};

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

```go v1_custom-domains_Add a custom domain_example
package main

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

func main() {

	url := "https://api2.freecustom.email/v1/custom-domains"

	payload := strings.NewReader("{\n  \"domain\": \"mail.acme.com\"\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_custom-domains_Add a custom domain_example
require 'uri'
require 'net/http'

url = URI("https://api2.freecustom.email/v1/custom-domains")

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  \"domain\": \"mail.acme.com\"\n}"

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

```java v1_custom-domains_Add a custom domain_example
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://api2.freecustom.email/v1/custom-domains")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"domain\": \"mail.acme.com\"\n}")
  .asString();
```

```php v1_custom-domains_Add a custom domain_example
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api2.freecustom.email/v1/custom-domains', [
  'body' => '{
  "domain": "mail.acme.com"
}',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);

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

```csharp v1_custom-domains_Add a custom domain_example
using RestSharp;

var client = new RestClient("https://api2.freecustom.email/v1/custom-domains");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{\n  \"domain\": \"mail.acme.com\"\n}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift v1_custom-domains_Add a custom domain_example
import Foundation

let headers = [
  "Authorization": "Bearer <token>",
  "Content-Type": "application/json"
]
let parameters = ["domain": "mail.acme.com"] as [String : Any]

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

let request = NSMutableURLRequest(url: NSURL(string: "https://api2.freecustom.email/v1/custom-domains")! 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()
```