Allow only authorized SMTP servers to communicate with your mail server
Last Updated: 10/3/2017 5053 Views 6 Users found this article helpful
Description

This article describes how to block all traffic from the WAN to an SMTP Server on the LAN or DMZ, except a range of IP Addresses on the WAN. This requirement usually arises when the user has a managed or hosted Spam Filtering service (eg. Postini) on the WAN and wishes to lock-down his incoming email to that service.

Resolution

Creating an Address Object for the IP Addresses of the hosted service:

Login to the SonicWall Management interface.
Navigate to Network | Address Objects.
Create a new Address Object with following values:
Name: Postini Network
Zone: WAN
Type: Network (This could be changed to Range or Host as required)
Network: 207.126.144.0
Netmask: 255.255.240.0

See the full Tech Document here:

https://www.sonicwall.com/en-us/support/knowledge-base/170503827035762