In our continued efforts to ensure high availability of our MAX MailProtection (formerly ControlEmail) solution, we have implemented some additional security measures that are designed to help secure our customers from the risk of emerging large-scale spam attacks.
Within our inbound message handling architecture, we have implemented a rate limiting system, similar to that used already for the outbound message processing. This will limit the number of messages each individual mail handling server will accept from a given sending IP address based on a configurable threshold of messages that if exceeded, will trigger a temporary deferral message. The risk of deferring legitimate mail by this technique is low. With rare exception, the only servers that send large volumes of email from a single IP address are either large-scale marketing systems, compromised systems used to disseminate spam, or other spam sources.
In addition, each inbound handler will track – based on each individual sending IP address – the percentage of suspicious mail (including spam, viruses, or blacklisted mail) detected, and will defer those senders with a very poor recent history.
These additional security measures are a reflection of our ongoing efforts to protect customers from email-borne threats.
Thanks for your attention.