Scenario 1 – LAN Mail clients (devices\application) addressing an internal mail server
In a scenario in which LAN Mail clients (devices\application) address an internal mail server, the basic assumption is that the LAN environment considered as a “safe” (isolated from the external network).
For this reason, the typical characters of the communication between the Mail enabled Devices\Applications, and the on-premises mail server is:
- Communication channel – mail-enabled Devices\Applications communicate with the On-Premises mail server using the SMTP protocol (non-encrypted connection).
- Authentication – most of the time, the Mail enabled Devices\Applications doesn’t use authentication mechanism (Anonymous authentication).
- IP Address restriction – in some scenarios, if the administrator wants to implement a basic security mechanism, the on-premise mail server is configured to accept anonymous SMTP connection only from a particular predefined IP address.