SAP Message XS837 - No delivery to &, as recipient cannot be reached at present

Diagnosis
The message could not be delivered to recipient &V1&. A temporary erroroccurred in the processing of the communication system (for example,hard drive is full).

System Response
Processing was completed normally.
Additional information on 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.