You can use SMTP authentication to allow remote users to send email using your MTA. Using SMTP authentication can introduce increased security risks if appropriate steps are not taken to ensure secure communications.
Symantec strongly recommends that you implement the following best practices if you are using SMTP authentication:
If you use SMTP forwarding, require TLS encryption for SMTP forwarding.
Do not attempt to use another Symantec Messaging Gateway appliance as your SMTP server for SMTP forwarding. SMTP forwarding is only performed over IPv4 addresses.
When configuring SMTP authentication mail settings, do not choose to accept authenticated mail connections from all IP addresses. Instead, specify a list of IPv4 and/or IPv6 addresses. This best practice may not be feasible for all organizations.
Configure and enable outbound filtering policies that protect against spam.