Hi,
As per my review on iRedAdmin Pro API docs,iRedAdmin don't have the option to disable user email account.
but it has the option to disable user email account in iRedAdmin console.

Please help me out how to disable a user email account via API.

Sample Code API for Deleting user email account:

public function delete_user ($API_HOST, $MAIL, $DAYS = NULL) {
      $curl = curl_init();
      if (!is_null($DAYS) && is_numeric($DAYS)) {
        curl_setopt($curl, CURLOPT_URL, "$API_HOST/user/$MAIL/keep_mailbox_days/$DAYS");
      } else {
        curl_setopt($curl, CURLOPT_URL, "$API_HOST/user/$MAIL");
      }
      if (!defined('COOKIE_FILE')) { define("COOKIE_FILE", dirname(__FILE__) . "/cookies.txt"); }
      curl_setopt_array($curl, array(
        CURLOPT_CUSTOMREQUEST => "DELETE",       
        CURLOPT_SSL_VERIFYHOST => false,
        CURLOPT_SSL_VERIFYPEER => false,
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_COOKIEJAR => COOKIE_FILE,
        CURLOPT_COOKIEFILE => COOKIE_FILE
      ));

      $response = curl_exec($curl);
      $err = curl_error($curl);
      curl_close($curl);
      $iredmail_response = json_decode($response);
      return $iredmail_response;
  }