Bulk email industry standards and best practices

Best practices to help bulk email you send to Yahoo email addresses get to your contacts.

SMTP error code table

Common SMTP error codes when sending messages to Yahoo Mail accounts, and why you would receive them.narrowed first column in table

Yahoo Outbound IP addresses

See the IP addresses that Yahoo Mail sends emails from.

DomainKeys Identified Mail and Yahoo Mail

Yahoo Mail uses DKIM to fight email forgery.

Yahoo Mail deliverability FAQs

Get the answers to commonly asked questions about email deliverability to Yahoo Mail accounts.

Yahoo DMARC policy

Learn why emails sent to Yahoo Mail accounts might be returned as a result of recent updates to Yahoo's DMARC policy.

4xx or 5xx SMTP error message notifications

Learn what causes SMTP errors and get tips for email administrators on how to troubleshoot them.

Yahoo Complaint Feedback Loop service FAQ

Get answers to the most common questions regarding the Yahoo Complaint Feedback Loop (CFL) service.

Guidelines for establishing SMTP connections to Yahoo Mail

4xx SMTP error codes

Learn what each 4xx SMTP error code means, and how you can prevent them from happening in the future.