When trying to route Notes mail from one Domino server to another on the same NNN it fails with the message on the sending server that it is not authorized to access the server on the destination server. The destination server log show Attempt to Access Denied.  This is an intermittent problem that will resolve itself (may be several hours later) without any changes being made. The sending server is in the LocalDomainServers and also explicitly named in the Access server field on the Server document for the receiving server. Its also not in any Deny Access lists but the fact that this is intermittent would suggest its not a simple issue of permissions.