We are making some changes to how email flows outbound from our mail servers. It is now necessary for digital.forest to implement OUTBOUND SPAM FILTERING. To date this has not been required, since as a rule our network is not a source of spam. Lately though we have had some problems with our servers being blocked by other mail providers. In one case this was directly attributed to a client's home computer being compromised and used to send spam. More often however it is caused by our clients setting their mail accounts here to automatically forward to another mail provider. If their account receives spam here, and forwards it, to the remote server it appears as if we are the spam source.

We have warned our clients about this many times, and even have temporarily implemented outbound filtering before; now we must take this step to protect all of our users.

We have actually been running the outbound filtering system for the past several days, but not blocking any mail, just collecting data in order to make a judgement on what needs to be blocked. This does introduce some latency in the mail delivery process, but so far we've been able to keep this delay to usually less than 5 seconds. After analyzing the data collected from around half a million messages, and load testing the filtering system with all of our production mail servers, we have a very good idea of both where the blocking thresholds need to be set to start, and what levels of latency are acceptable. Effective immediately we will start blocking messages at a relatively high "spam score" threshold of "20" and gauge the impact of that action on the mail servers, the filtering systems, and our ability to deliver mail to domains that consistently give us problems (Comcast, Hotmail/MSN, Shaw, Yahoo, etc.) If all goes well we will slowly lower the thresholds until we achieve a balance of the right scores and performance.

The ultimate goal is to increase the reliability of mail delivery, and prevent our servers from being blacklisted by other mail providers. If you have any questions or mail-related problems that you believe are attributed to this change, please contact our Technical Support group via a trouble ticket.