Yahoo mail domains are starting to embrace DMARC more explicitly. You may have seen an increase in bounce messages with the following explanation:
"554 5.7.9 Message not accepted for policy reasons. See http://postmaster.yahoo.com/errors/postmaster-28.html"
This is because Yahoo no longer accepts messages where the From domain is a Yahoo mail domain, and the message originates from a non-approved Yahoo mail domain server/service. This is a security measure they have implemented to help reduce potential address spoofing of their mail domains.
What this means: You can no longer send with the From address set as anything from a Yahoo address when sending to a domain that checks DMARC before accepting mail.
What you can do: You will need to change the From address to a non-Yahoo address. We recommend using your own mail domain, or one you control that is legitimate. You can then set the Reply-To field to be the original Yahoo address that previously was used in the From field.
What about these messages, are they lost? : Yes, any send with this bounce message is discarded and tracked as a Block. You will need to adjust your From address field settings, and then try resending from your side.
28 March, 2016
Yahoo has updated their DMARC policy to utilize p=reject for the below low-volume Yahoo international domains. Please make any changes you need to handle these domains in the same way you handle yahoo.com.
As a reminder, this change means that you will not be able to send with a from address of any of the following domains: