Fix: Yahoo and Hotmail not receiving my emails

Background: I have an auction site that sends opt-in only emails, when people sign-up, but Yahoo still isn't recognizing it as a valid sender. Gmail receives email from my domain but Yahoo and Hotmail do not, and auto-bounce emails. For Yahoo, Error: 421 4.7.0. [XXX]. Goal: Yahoo and Hotmail users must be able to receive my emails. Suggested tasks based on Yahoo which may or may not solve the problem: DKIM authentication Publish reverse DNS records BE Can-Spam DMARC Compliant Establish Compliant Feedback loop w Yahoo, Hotmail and Gmail Limit messages to send per SMTP connection to 20 basically everything relevant here: [login to view URL] Etc that can help to solve problem Restrictions: I currently use Zoho to host some of my emails. This shouldn't change. We use the same email address (no-reply@domainname) for mailchimp as well as these email addresses. This should not change