Messages sent to Yahoo email addresses fail authentication checks and are rejected with temporary status codes, this results in the email being placed in the delivery queue for retry. Such messages typically remain in the delivery queue until they expire.
Yahoo uses a policy which may block or delay email that do not use sender authentication methods, such as SPF, DMARC, and DKIM or have not correctly configured their reverse DNS records for their domain.
Symantec does recommend the addition of SPF, Sender ID, DKIM, and DMARC records in DNS to validate mail delivery. These technical controls act to both protect the reputation of your IP/domains while also meeting the expectations for standards with a growing number of recipients.
Symantec offers Email Fraud Protection, which is a product that automates the configuration and monitoring of sender authentication for SMG and various cloud and email services. For more information, please seeSymantec Email Fraud Protection.