How to Get Email Delivered to Yahoo | How Yahoo Filters
The key mission of Yahoo is to deliver messages that people want to receive and filter messages they don’t. With Yahoo, you’ll need to perform list management tasks frequently and monitor hard & soft bounces as well as inactive subscribers.
Sending emails to users who aren’t reading them or who mark them as “spam” will hurt your delivery metrics and reputation. Send email only to those who want it. Use an opt-in method of subscription for your mailing list and make sure subscribers have verified their intent to receive your mailings.
Review email content for common characteristics of spam. Test your emails’ visual look with image placeholders. Many of your recipients won’t see images in your email. Email on Acid is an excellent place you can go to check your message rendering.
Make sure you are linking to domains, not IP addresses. Yahoo will filter out these links.