Message Not Delivered: Message sender blocked by receiving server
The message could not be delivered because the recipient's email provider is not accepting messages from this sender. This usually means that the receiving system has security or policy concerns with regard to either the specific sender, recipient, or the sender's email system.
Retry the email message see if it was a one-time problem or if the same error occurs.
Otherwise, contact the sender's email support team as the email system may have a security issue. This typically requires helpdesk support.
5.7.1: Official Definition
A permanent failure is one which is not likely to be resolved by resending the message in the current form. Some change to the message or the destination must be made for successful delivery.
The sender is not authorized to send to the destination. This can be the result of per-host or per-recipient filtering. This memo does not discuss the merits of any such filtering, but provides a mechanism to report such. This is useful only as a permanent error.