Message Not Delivered: Message routed to non-email system
The message could not be delivered because the recipient's domain is not set up to handle email.
Check your recipient's domain in the recipient's email address for misspellings or missing letters. If an error is found, correct it in contacts list or address book for next time.
If necessary, contact the recipient another way (e.g., phone or text message) to confirm their email address.
5.1.9: 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 mailbox address specified was valid, but the message has been relayed to a system that does not speak this protocol; no further information can be provided.