To relay mail outbound through SpamTitan, you have two options
Option A - Outbound mail from trusted mail servers.
For mail servers, from a SpamTitan point of view, you just need to do the following:
1. Specify the IP addresses that will be sending mail in System Setup -> Mail Relay > Outbound > Trusted Networks. This basically tells SpamTitan what IP addresses it will relay mail outbound for.
2. Specify the same list on the Anti-Spam Engine -> Settings > Internal Networks. This allows mail coming from these networks to be treated more favourably when it comes to spam testing.
3. Configure the outbound mail policy. This is done by going to the AntiSpam Engine > Domain Policies tab. Select 'Outbound Mail' from the list. Then set the spam and virus filtering to what you please. We would recommend that the 'spam threshold' for outbound mail be set higher (e.g. 8) to avoid false positives as it is mail from a trusted source.
4. Configure your mail server/s to use your SpamTitan server as a smarthost. i.e. direct all outbound mail to your SpamTitan server.
Option B - Outbound mail from remote users
For remote users, you use SMTP/SASL. This is enabled via SMTP/SASL Authentication in the System Setup > Mail Relay > Outbound tab in SpamTitan. Once this is set up correctly you don't need to specify IP address in Trusted Networks as this is only used for your internal Mail Server if you want to send mail out via SpamTitan.