Occasionally, email providers block unrecognized IP addresses to prevent spam. If this happens, Poloniex receives a message that your email provider did not accept the email, and we send a request for our IP address to be allowed. 

While we act quickly to submit the request, the issue is dependent on your email provider’s response time. If you don’t receive a Withdrawal Confirmation email in 48 hours, please open a support ticket at Poloniex Support