Default Receive connectors in Exchange Server 2016

Understanding default Receive connectors in Exchange Server 2016 Mailbox Server

About 5 receive connecters are created by default 3 with frontend Transport role and 2 with hub transport role.

Frontend Transport

•       Client Frontend - 587
•       Default Frontend – 25
•       Outbound proxy Frontend - 717

Hub Transport

•       Default - 465
•       Client Proxy - 2525

Receive connectors in the Front End Transport service

Receive connectors in the Front End Transport service are responsible for accepting anonymous and authenticated SMTP connections into Exchange organization.

          TransportRole attribute is set to FrontendTransport on these connectors.

The Front End Transport service relays or proxies connections to the Transport service for categorization and routing to the final destination.

Default Frontend: This is the common message entry point into the exchange organization, this connecter receives anonymous connections from external SMTP servers on port 25

Supports authentication mechanisms as (TLS, basicAuth, BasicAuthRequireTLS, Integrated, ExchangeServers)

Outbound Proxy Frontend: This connecter accepts authenticated connections from the Transport service on port 717, connections are encrypted with the Exchange server's self-signed certificate, This connector is used only if the Send connector is configured to use outbound proxy.

Supports authentication mechanisms as (TLS, basicAuth, BasicAuthRequireTLS, Integrated, ExchangeServers)

Client Frontend: Receive connection from authenticated SMTP clients on port 587.

Supports authentication mechanisms as (TLS, basicAuth, BasicAuthRequireTLS, Integrated)

Default Receive connectors in the Transport service or (aka HUB Transport or back end transport as it do not accept connect from clients)

Receive connectors in the Transport service are responsible for accepting authenticated and encrypted SMTP connections from other transport services on the local Mailbox server or remote Mailbox servers in your organization.

The TransportRole attribute is set to HubTransport on these connecters. Clients don't directly connect to these connectors.

Default:  Port used 2525

Accepts authenticated connections from

•      The Front End Transport service on the local or remote Mailbox servers
•      The Transport service on remote Mailbox servers
•      The Mailbox Transport service on the local or remote Mailbox servers
•      Edge Transport servers

The connections are encrypted with the Exchange server's self-signed certificate.

Supports authentication mechanisms as (TLS, basicAuth, BasicAuthRequireTLS, Integrated, ExchangeServers)

Client Proxy: 465

Accepts authenticated client connections that are proxyed from the Front End Transport service.

Supports authentication mechanisms as (TLS, basicAuth, Integrated, ExchangeServers)