How to limit inbound emails to some ip addresses and still allow mobile users to send emails via the Symantec Messaging Gateway (SMG) after authentication
click on "Administration" > "Configuration" > YourHost > "SMTP"
activate "inbound and outbound filtering"
note: to use SMTP Authentication "outbound filtering" has to be enabled. So you must use the option "outbound filtering only" or "inbound and outbound filtering".
Under section "Inbound Mail Acceptance" enter the IP addresses of hosts from which you want to receive emails (e.g. your ISP servers)
Under section "Authentication Mail Settings" activate "Enable Authentication"
Configure this as your system requires. Further information can be found in the online help or in the "Administration Guide" (page 140 and below)
You have a requirement to limit receiving emails to only a few specific servers
You need to enable mobile users to send emails via the Messaging Gateway.