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Marking some mail as spam • Greylisting • Blocking sites that spam our campus
The UW-River Falls email system filters email for spam. Spam is currently filtered through the use of the SpamAssassin software package. If you are interested in the details, you may visit the SpamAssassin web site. SpamAssassin uses many different methods to find spam email, including looking in databases, analyzing the headers of the email, and analyzing the body text of mail. Detecting spam is more of an art than a science. Rather than risking marking mail as spam that is really not spam, we have attempted to err on the side of not marking mail as spam when in doubt. Mail that is judged to be spam will be marked by putting in special email headers. This email can then be filtered automatically by a mail filtering rule, which can either put the mail in a separate folder, or (if you choose) delete the mail immediately. IT Services recommends moving this email into a separate folder, rather than deleting it, so that you do not lose any important email by accident. If no mail filter rules are set up, you will receive the spam mail normally, but the subject line will be marked so you can easily determine that the mail is likely to be spam.
The email headers inserted in the email which look like this:
X-SPAM-Score: 8.6 (******)
X-Spam-Warning: Yes
The number of stars corresponds to the spam score. So, for example, a spam score of 8.6 will yield 8 stars. The X-Spam-Warning is set to "Yes" if the score exceeds a certain threshold (determined by IT Services and may be changed depending on performance of the software). These headers will be placed in all email that have a SpamAssassin score above 0.
You will occasionally receive some non-spam email that will be marked as spam, and some spam that is not marked. This will always be the case, as it is difficult to guess which email will be considered spam by a particular recipient.
If you would like assistance in setting up an email filter to deal with spam, please send us a request.
IT Services has also implemented a process known as greylisting, which is a relatively new method of combatting spam. More information can be found on the greylisting website. Greylisting works by generating a temporary failure error before allowing delivery. The first time the off-campus site tries to deliver the message, the UW-RF mail system will report a temporary error to the delivering site and keeps track of where the site is (IP address), who the message appears to be from and who it is addressed to. Since the error was temporary, the off-campus site should make another attempt after some delay. The second time the delivery is attempted, the UW-RF mail system recognizes that it is a second attempt based on the information it tracked at the first attempt and allows the off-campus system to connect and deliver the email. Information about successful deliveries are kept for 10 days, so subsequent deliveries with the same sender and recipient coming from the same site during that period won't be delayed by this process.
This method is effective since most spam-sending sites do not bother making second attempts to deliver a message if there is any sort of failure on the first attempt. However, it may result in some delay of emails coming in from off-campus sites (including legitimate ones). The delay is determined by the setup of the off-campus site and not something UW-RF has control over. If you fill out a form on a website that results in an email to you(such as a site password reminder), it is not unlikely that there will be a delay in receiving the email.
Some off-campus sites send huge amounts of unsolicited email to our domain. They are often sent to non-existent UW-River Falls email accounts. Handling this email slows down our mail server. When this unsolicited email actually is deliverable, it is widely viewed as an annoyance and time-waster by those who do receive it. For these reasons, and in order to increase the responsiveness and usefulness of our campus email system, we will not accept email from some sites that send us very large quantities of unsolicited messages. Most of the sites we block are blocked because we subscribe to select services that provide the names of currently-spamming mail servers.
If you have concerns or questions about the way UW-River Falls handles spam, please give us your feedback.
IT Services Spam policy
General email support
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