Thank you for writing to Yahoo! Mail.
Please note that if you are not the mail server administrator for the
mail server(s) affected, we encourage you to contact the administrator
so they can address the possible issues regarding mailings from the mail
server. We also appreciate your report as your input helps us to
identify ways to constantly maintain and improve our service. We
apologize for any inconvenience this has caused you.
If you notice any further difficulties when delivering to Yahoo! Mail
accounts, after waiting a reasonable amount of time, please let us know
by replying directly to this email. However please note the following:
If you are receiving the error code "421 Message from x.x.x.x
temporarily deferred" or "451 Message temporarily deferred - 4.16.50" in
your SMTP logs, this indicates that the message you attempted to send
was not accepted by Yahoo! Mail servers. It is not a permanent error;
your system will automatically re-try later. If, after attempting to
deliver to Yahoo! and receive the 4.16.50 error repeatedly and conform
to the best sending practices outlined in the following page, we
encourage you to apply for prioritized sending at the link below.
Recommended Best Practices:
Yahoo! Mail ISP Issues Form
Prioritized Delivery (Please note that this form can also be used by
senders whose mailings are being directed to the Bulk Folder):
Yahoo! Mail Bulk Sender Form
If you are receiving a separate error than that above, please provide
the text of any error messages you may have received. Also, providing
the specific IP address of the mail server that experienced the delivery
issue will help us to troubleshoot the issue more efficiently.
For assistance with delivery issues to Yahoo! Mail, please visit:
Mail
We appreciate your patience while we work to improve and maintain our
service.