SAP Message AM235 - Reason for Undeliverability & Is Not Valid

Diagnosis
The key &V1& is not defined in table TSAD12 as a reason fornon-delivery.

System Response
The address is incorrect and is not accepted.

Procedure
Specify a valid reason for non-delivery or maintain the missing entryin Customizing.
You can maintain reasons for non-delivery in Customizing withtransaction SA18.