Iteratively failure to deliver message

Tonight, we experienced megabytes and megabytes of this in the logfile:

Initially, we assumed that the domain was being flooded. However, connections were not created. This might be a problem related to:

• a local user attempting to send a message stanza to a federated user

• an outgoing session to the domain of the federated user cannot be created

• as a result of an error message is sent back to the local user

• the local user isn't available

• causing an error message to be snet to the federated user

lather rinse repeat