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Exchange 2016 + 2019 Mail Flow with Ports

The information provided is valid for Exchange Server 2016 and Exchange Server 2019.
Last updated: 2021-06-10

Microsoft Docs provides detailed documentation on modern Exchange Server mail flow and the transport pipeline. That article helps you to

The detailed diagram showing the Exchange Server 2016 transport pipeline in the TechNet documentation does not show the TCP ports being used by the Exchange Server 2016 components.

The following diagram is an updated version of the original diagram showing the TCP ports being used by

  • Front End Transport service
  • Transport service
  • Mailbox Transport service
  • Mailbox Transport Delivery service

Exchange Server 2016 Mail Flow with Ports

By default Exchange Server implements the following receive connectors

  • Front End Transport service
    • Default Frontend SERVER, TCP 25
    • Outbound Proxy Frontend SERVER, TCP 717
    • Client Frontend SERVER, TCP 587
  • Transport service
    • Default SERVER, TCP 2525
      Server SMTP connections connected to TCP 25 are proxied to this connector
    • Client Proxy SERVER, TCP 465
      Client submission connections connected to TCP 587 are proxied to this connector
  • Mailbox Transport service
    • SERVER\Default Mailbox Delivery SERVER, TCP 475 (hidden)

Cross-server SMTP communication occurs on either TCP 2525 or TCP 475.




Enjoy Exchange Server!



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    Supervisión de Exchange: ¿Qué es el flujo de correo?
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