Symantec Messaging Gateway (SMG) 9.5.4 running on ESXi Server 3.5 needs to be updated to SMG 10.0.0 or later but SMG 10.0.0 is only supported on VMWare ESXi 4.0 or greater and it is unclear whether to update the virtual infrastructure or SMG software first.
The supported update order when migrating from SMG 9.5.x to SMG 10 when running on virtual infrastructure earlier than ESXi 4.1 is as follows:
1. Shut down the SMG virtual machines 2. Update the VMWare installation to ESXi 4.1 or later 3. Restart the SMG virtual machines 4. Update SMG to the latest release via the Control Center Administration->Version->Updates page
SMG 9.5.x will run without issue on ESXi 4.1 or later and so the underlying VMWare installation should be updated prior to updating the SMG virtual machine software.
For reference, the SMG version / supported VMWare matrix is as follows: