If you want to keep your IPs off of IP blacklists, it's important to police your users. Compromised users quickly ruin the good reputation of an IP address, leading to listings on public RBLs like Spamhaus and UCEPROTECT (if you're lucky), or - worse - degraded reputation in commercial anti-spam systems and services. Policing your users effectively requires vigilant monitoring of user behaviour over time, detecting when that behaviour has started to go "bad", and then taking appropriate actions to limit the bad behaviour.
Today we're happy to announce Policy Scripting, a powerful new feature of the MailChannels platform which allows you to create sophisticated policies in a high level programming language. Policy scripts are executed in real time as email is transferred through the MailChannels system, and have access to the full state of the SMTP session, in addition to any content filtering analysis results and the full sending history of the user responsible for the message. Limit abuse by cutting off sending privileges for users who have sent more volume than normal, or who have attempted to deliver to too many invalid recipients (a sign of a "dictionary harvest attack" - a common spamming technique).
There is lots more to it than a blog post can cover. If you're a customer, contact us for details.
We are excited about how our customers are using the Policy Scripting system, and look forward to adding new features in the coming months that will bring even more tools for behaviour analysis and anomaly detection.