Small businesses are experiencing deliverability problems to Yahoo email addresses after Yahoo updated its email authentication policy this week. Stricter rules around using third-parties has had some marketers reporting bounces. "We are currently experimenting with an anti-abuse technology that helps us protect our users from phishing and spoofing attacks," Yahoo told MarketingLand. "As a result of this experiment, a small percentage of our users who use service providers external to Yahoo may experience issues."