For your Exchange Server to be able to be visible and accessible from the Internet you need to configure a few things as listed below:
You need to create an MX record so that mail knows how to get to your organization. In this example, we will point our send connector to Office 365 DNS as this is where the record is located.
Launch the Exchange Admin Center (EAC) and navigate to Mail Flow > Send Connectors and then click the + button to create a new connector:
A new window will appear. You need to enter the following information:
Click Next to continue...
As we are using MX records specified in DNS we chose this option but your ISP will ask you to select a smart host and they will provide you with the smart host information. Click Next to continue.
Here you need to enter in your Address Space information, click the + button to capture the info, a new window will appear as shown below:
We used * in the FQDN, click Save to go back to the previous screen and then click Next to continue.
You will be asked to select a source server in the next screen, click the + button to select the Exchange Server you want to be used in this send connector.
We chose the Exchange 2019 server as that is where the certificate was created.
Click the server and then click the Add > button to add it to the box and then click OK to go to the previous screen.
As you can now see the server we chose is listed above, click the Finish button.
Back in the EAC, you will now see the connector you created as well as the status which is Enabled and the Maximum default size of 35MB.
The next section we will look at is the receive connectors. We need to allow the server to receive mail from the Internet.
In the Exchange Admin Center (EAC), click on mail flow > receive connectors.
You will notice that for each server, Exchange 2013 and higher, you have five connectors. The one we are interested in is the Default Frontend <ServerName>.
If you double click that connector, on the general page you can make changes like the maximum receive size and hop count, etc. The page we are looking at is the Security one. Click the 2nd Tab on the left called security as shown below:
If you scroll down you will see that Anonymous users is ticked, don't panic, this is so you can receive mail from the Internet. It does not open you to open relay.
Lastly, let's take a look at Accepted domains. In these tutorials, we created our domain as collaborationpro.com which was the actual domain name valid on the Internet so the accepted domain is correct. However, in your environment, you might have domain.local which is not valid and will need to create a new Accepted domain.
In the same place as the Send and Receive connectors, click on Accepted domains and then click the + button to add a new accepted domain:
A new window will pop up where you need to enter the following information:
Click Save to finish your Setup.
In the next article in the series, we will look at the following: