Following the update to Messaging Gateway (SMG) 10.6, a large number of DNS resolution failure messages appear in the maillog file.
2015 Dec 2 12:03:39 PST (notice) ecelerity: [30987] DNS resolution failure 7c1767b30512b6003fd3c2e618a86522.smg.ultra.brightmail.com: 4
The DNS queries performed by the "ultra" URL filtering generates a NOTICE level message when the hostname queried does not exist in the DNS or the DNS query times out.