This can be a particular problem with websites that require an account to be created and the email address confirmed before they can be used – or when a user of a greylisting mailserver attempts to reset their credentials on a website that uses email confirmation of password resets. If the sending MTA of the site is poorly configured, greylisting may delay the initial email link. In extreme cases, the delivery delay imposed by the greylister can exceed the expiry time of the password reset token delivered in email. In these cases, manual intervention may be required to whitelist the website's mailserver so the email containing the reset token can be used before it expires.