Messaging Gateway (SMG) does not use secure DNS (DNSSEC) in any configuration and will not be directly affected by changes to the root zone key signing key (KSK).
In its default configuration, SMG communicates with the customer DNS infrastructure in a "forwarder" configuration i.e. SMG maintains a local DNS cache but relies on the customer DNS servers for DNS lookups. While SMG will not be directly affected by the change to the root key rollover, customers which make use of DNSSEC may indirectly impact SMG operation to the extent that their own DNS servers are impacted by the change to the root key rollover.
Please see the following for more information on the Root Zone KSK Rollover: