SAP Message XS809 - No delivery to &, as recipient cannot be reached at present

Diagnosis
The message could not be delivered to recipient &V1& as the recipientcannot be currently reached at this address.

System Response
Processing was ended normally.
Additional information of the node used (in the system language of thenode, if available):
V4

Procedure
The system will automatically send the message again. If the messagecan still not be delivered after a specified number of attempts, therecipient list of this message <(>&<)>V1& is flagged as Unreachable.
Check the recipient address. Try sending the message again later.