To ensure that our products perform at consistently high service levels, we set both a rate limit and a timeout value.

The API tends to respond in 3-5 seconds to each request you send. However, since we are sending a live ping to check the email address sent for validation, it can sometimes take longer for the response to be returned. The maximum time we allow is 15 seconds for each call that is submitted to the API. If we cannot determine the correct response in this time, you will receive an HTTP status code of 500 (note that you are not charged for these responses).

You also have the option of controlling the timeout value yourself: the timeout parameter lets you specify the number of seconds you are willing to wait before a response is returned. If you select a value between 3 (minimum acceptable) and 15 and a timeout occurs, a confidence status of "unknown" and a verbose result of "timeout" will be returned (note that you are not charged for these responses).