The Hub Transport Server role is deployed inside your organization’s Active Directory. This server role handles all internal mail flow and is also responsible for applying transport rules as well as journaling policies to the respective messages flowing through your organization.

Mail flow issues — Define connectors. Transport rules. Ethical firewall.

A Hub Transport Server handles internal mail flow. This varies based on deploying an Edge Transport server as the Internet-facing SMTP server in your DMZ.

If you use an Edge Transport Server, all inbound and outbound e-mail will pass through the Edge Transport Server. Opting not to deploy an Edge Transport Server enables the Hub Transport Server to function as the Internet-facing SMTP server, though it’s not advisable.

When you encounter this problem on installing Exchange 2007, " was run: "Service 'MSExchangeTransport' failed to reach status 'Running' on this server.".

This is a quick fix to it:
– Enable IPv6 in and disable IPv6 in registry, here are the steps below.

Hub Transport Server: Steps to disable IPv6,

Step 1. Launch registry, click on
– HKEY_LOCAL_MACHINESYSTEM
– CurrentControlSetServicesTcpip6Parameters. In the details pane,
– Click New, and then click DWORD (32-bit) Value.
– Type “DisabledComponents” (without quotes) and then press enter.
– Double-click DisabledComponents and type 0xffffffff in Hexadecimal or 4294967295 in Decimal and close the registry editor.

Step 2. Now, navigate to C:Windows/System32/Drivers/etc ,

Open the host’s file in notepad and delete the IPv6 entry associated with it and start the installation process again.

Note: This error occurs when the “Hub transport role fails” prompting an error “MsExchange transport failed to reach status running on this server”. Mailbox & CAS installations are canceled as well