Why does using an AOL or Yahoo address cause bounces?

This year, Yahoo and AOL stepped up to combating spam being sent on the internet. Yahoo and AOL do this by changing how they authenticate emails being sent from their address. They no longer allow their users to send using 3rd party services, such as Benchmark Email, Constant Contact, and MailChimp. To prevent getting your emails bounces, we suggest using an email address other than Yahoo, Rocket Mail (owned by