What’s new in Exchange 2013 transport services? Let’s take a look.
Due to the change in the architecture and number of roles in 2013, there are three main transport services – one on the CAS and two on the mailbox. They are
- Front End Transport Service on CAS role
- Transport Service on Mailbox and
- Mailbox Transport Service on Mailbox role, which is further split into Mailbox Transport Delivery & Mailbox Transport Submission Service.
Let’s take a look at each of these services in a bit more detail and find out what they are responsible for.
Front End Transport Service:
- Runs on all CAS servers.
- Is a stateless SMTP service.
- Doesn’t queue or store any data locally.
- Is a stateless proxy for all incoming emails from all types of clients.
- Can be configured as a proxy for outbound emails if required.
- Only communicates with the Transport Service on the mailbox role.
Transport Service:
- Runs on all mailbox servers.
- Equivalent to the transport service on previous hub roles.
- Receives & deliver all inbound emails to the organization.
- Submits & deliver all outbound emails to the organization.
- Performs all message processing in the transport pipeline.
- Does queue messages locally, which can be stored on your system drive.
- Unlike transport service in previous versions of Exchange, this service does not communicate directly with the mailbox database (which is handled by Mailbox Transport service).
- This service communicates with the Front End Transport service on the CAS and the Mailbox Transport service on the mailbox role.
Mailbox Transport Delivery Service:
- Runs on all mailbox servers.
- Does not store or queue data locally.
- Receives SMTP messages from the Transport service and connects to the mailbox database (using RPC) to deliver the email.
Mailbox Transport Submission Service:
- Runs on all mailbox servers.
- Does not store or queue data locally.
- This service connects to the mailbox databases using RPC to retrieve emails and submits them to the Transport service over SMTP.
Hope this shed some light into the new transport architecture in Exchange 2013.
