What are your policies on spam filters and automated spam challenge / response filters like Earthlinks and SpamArrest?
All confirmation techniques that require responses to emails are honored by hand in a timely fashion by us – there is no further interaction required by publishers or readers. It’s a service we’re happy to provide. But, if an email address repeatedly issues challenge / response messages, indicating that the end-user is clearly not approving FeedBlitz emails, they will be deleted.