Exchange Server 2016 send/receive from Office 365 via SMTP Server

Hi Hieu_Vu,

it is possible to establish mail communication between Office 365, Exchange Server, and an SMTP server. Below are general steps that can guide you through the process:

1. Define Your Scenario:
   Determine whether it's an internal relay (for devices and applications communicating with internal recipients) or an external relay (for those communicating with external recipients).

2. Authentication Consideration:
   Decide whether devices and applications will authenticate or connect anonymously.

3. Configure TLS for Authenticated Relay:
   If using authenticated relay, set up the TLS certificate for the client front-end connector.

4. Configure Anonymous Relay:
   For anonymous relay, create a new receive connector restricted to specific remote IP addresses.

5. Enable Mail Flow Between Microsoft 365 and SMTP Servers:
   If needed, enable mail flow between Microsoft 365 or Office 365 and any SMTP-based email server like Exchange or a third-party server.

You can check these links for more info;
practical365.com
Set up connectors to route mail between Microsoft 365 or Office 365 and your own email servers | Microsoft Learn