Gateway Spam Filtering

CSLab's mail system can automatically filter spam for you in a number of ways, for your own personal address and for your mailing lists; you can use different settings on different mailing lists and on your own address. This filtering is managed through our self-serve email anti-spam settings pages.

We support a number of options for this filtering:

  • No automatic system spam filtering

    No automatic spam filtering will be done, just the standard PureMessage spam tagging and virus removal. You can use personal email filters to do any filtering that you want.

  • Moderate (system) spam filtering

    The system will automatically reject email that it feels has a high chance of being spam. Because we reject it, senders will always get notified that their message did not get through.

  • Strong (system) spam filtering

    The system will reject or discard email that it feels is spam. Senders will not always get notified that their message did not get through.

  • Only accept email sent from DCS computers

    We will only accept email for this address from machines that we consider to be inside the Department of Computer Science (including teaching lab accounts, DGP, and so on, not just CSLab-managed machines); email from other machines will be rejected. Senders will always get notified that their message did not get through.

  • Only accept email sent from University of Toronto computers

    This is as above, but for University of Toronto machines instead of just DCS machines.

It is important to note the difference between machines and people; for example, someone in the department might send you email from a Google Mail account, and that would be considered to be outside the department because GMail's mail machines are not inside the department.

For moderate or strong filtering, you can opt to have email sometimes be delayed in order to get less spam. In addition to sometimes delaying email to your address, it is possible for a sender's email system to dislike this and to fail to deliver the message; if this happens, the sender should be informed about it.

(If you are familiar with email anti-spam technology, this is known as 'greylisting'.)

Messages that are automatically filtered out by the mail system will not be put in your oldmail.

The specific techniques that we use to implement moderate and strong filtering may change over time. We guarantee that moderate spam filtering will only ever use techniques where the sender is informed if their message doesn't get through. With strong filtering, there is no such guarantee, although we will try to have senders informed as much as is practical.

We feel that moderate spam filtering (with or without delaying email) is pretty safe and quite effective. Strong mail filtering is more dangerous since if a message is mis-classified as spam (which does happen from time to time), no one will ever know about it.