• Open Exchange Admin Center and Navigate to Mail Flow > Receive Connectors
• Create a new Receive Connector with following settings:
  • Role: Fontend Transport
  • Type: Custom
    

• Network adapter bindings: All available (IPv4)
  
• Remote network settings: [IP address of the device(s) that will be sending emails]
  
• Finish
• Open the new connector and modify settings in Security tab:
  • Authentication: Externally secured
  • Permission groups: Exchange Servers and Anonymous users
    

February 2018
Windows Server 2016
Microsoft Exchange 2016