SAP Message WZ335 - Inbound distribution could not be entered

Diagnosis
An attempt was made to enter the Internet mail address of the user usedfor the logical RFC destination WORKFLOW_LOCAL_ccc (ccc to be replacedwith the current client) for inbound distribution.
It was possible to establish this Internet mail address, but an erroroccurred inserting into inbound distribution.

System Response
The system rejects the entry.

Procedure
Someone else may be trying to make an entry. Try again later.