Department Email
Anti-Spam
The server uses SpamAssassin to mark messages as either spam or non-spam. No emails are actually blocked, users must use filters to either delete spam or move it to a separate folder.
All messages will be marked with X-Spam-Score and
X-Spam-Flag headers. The X-Spam-Score header looks
like this:
X-Spam-Score: 7.04 (*******) DNS_FROM_AHBL_RHSBL,MISSING_SUBJECT
The number represents how "spammy" the email is. As a general
rule, anything 4.5 or higher is probably spam and anything above 10 is
definitely spam. However, users can decide on their own threshold
based on their experience. The asterisks represent the integer portion
of the number. This allows email client with limited filtering
capabilities to make use of the tag. The text that follows the
asterisks is a list of SpamAssassin rules that the email
matched. These are of little use to the user, but can help the network
administrators debug false positives and negatives.
Some email clients can only filter on fixed strings. The X-Spam-Flag header is set to YES when the email has a score greater than or equal to five. It is set to NO when the score is less than five.
Using a threshold of 4.5, the accuracy of the spam filter is very good. Tests done by the SpamAssassin team show that, on average, for every 10,000 non-spam messages, 3 of them will be labeled as spam, and for every 1,000 spam messages, less than 25 of them will be labeled as non-spam.
Users that experience false negatives (spam marked as non-spam) or false positives (non-spam marked as spam) should bounce (not forward) them to spamtrap@tim.cs.olemiss.edu. They can be used to improve the accuracy of the spam filter. For instructions on bouncing email from your email client, please see this page on the SpamAssassin web site.
Users that need assistance setting up their spam filters on their email client should contact a department network administrator.