Mail1 Blocked on Yahoo!

Getting a 421 4.7.1 bounce when sending mail to Yahoo! accounts:

http://help.yahoo.com/kb/index?page=content&y=PROD_MAIL_ML&locale=en_US&id=SLN3436&impressions=true

Request you to open support ticket with mention domain name and bounce message. So we can check and get back to you on ticket.

Support ticket submitted.

Thanks for your co-operation.We are working to resolve your issue as immediately as possible and update you back on ticket.

I am also getting NDRs for messages to Yahoo addresses. Should I open a ticket as well?

We're aware of the concerned issue and working on it. However, if you'll open a support ticket then we'll update you on it as soon as the issue will be fixed.