const options = {
  method: 'POST',
  headers: {'X-API-Key': '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({item: '<string>'})
};

fetch('https://api.mailchannels.net/inbound/v1/users/{email}/lists/{listname}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.mailchannels.net/inbound/v1/users/{email}/lists/{listname}"

payload = { "item": "<string>" }
headers = {
    "X-API-Key": "<api-key>",
    "Content-Type": "application/json"
}

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

print(response.text)

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.mailchannels.net/inbound/v1/users/{email}/lists/{listname}",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'item' => '<string>'
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "X-API-Key: <api-key>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

curl --request POST \
  --url https://api.mailchannels.net/inbound/v1/users/{email}/lists/{listname} \
  --header 'Content-Type: application/json' \
  --header 'X-API-Key: <api-key>' \
  --data '
{
  "item": "<string>"
}
'

{
  "item": "<string>",
  "item_type": "<string>",
  "action": "<string>"
}

{
  "errors": [
    "<string>"
  ],
  "code": 123,
  "message": "<string>"
}

{
  "errors": [
    "<string>"
  ],
  "code": 123,
  "message": "<string>"
}

{
  "errors": [
    "<string>"
  ],
  "code": 123,
  "message": "<string>"
}

{
  "errors": [
    "<string>"
  ],
  "code": 123,
  "message": "<string>"
}