Mx Record :
Please point your MX record to the Inbound MX provided when registering for HES. It will look something like below:
If your domain is "domain.com", your inbound mx record will be similar to domain-com.snwlhosted.com (NOAM customers) or domain-com.snwlhostedeu.com (EU customers)
Configure HES to allow all Emails to be routed through HES to your Mail server (Mail Server public Ip ) ( Inbound)
NOTE:Â Please add your mail server's FQDN or IP and no other IP in the text box (No ISP IPs or other external domains Public IP address)

You are now configured to have inbound traffic routed form the internet to deliver to HES for domain.com that will then to you Public IP set for your mail server, which your firewall will nat and send the traffic to your internal IP address of your mail server to receive the inbound emails.
Be sure to have the Inbound Auditing on HES to track the inbound message being scanned by HES and delivered to O365.Â
On the message audit page, click Settings

 Ensure the 'on' radio button is selected for Auditing inbound email
