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Durham University

Computing and Information Services

Junk mail and spam

Junk mail filtering on exchange (September 2010)

In addition to the policy on the Mail Gateway detailed below, Microsoft Exchange performs further filtering on mail received from outside and places mail suspected to be junk in the users 'junk email' folder. Occasionally genuine email will be wrongly identified as junk and users are therefore advised to monitor their junk email folder in order to identify wrongly classified messages and mark the senders as safe.

Email sent within Exchange from user to user is not subjected to this extra filtering.

Stronger spam email action (March 2005)

In accordance with IT Strategy policy (minute 24(e),, a revised method for dealing with spam email has been adopted by the CIS mail gateways systems since Easter 2005. In addition to the user selectable method for filtering mail by a 'mid-range' spam score, an additional 'top-range' score has been introduced above which email will be discarded automatically. Unlike the existing opt-in filter mechanism, this top level discard will be an opt-out approach. In effect it will divide the spectrum of email spam score into three bands; a top band which will be automatically discarded, a mid range band which can be discarded or filtered into folders at the user's choice, and a low band which is assumed to be valid email and appears in the users inbox.

Trials of this approach indicate that 30-40% of email which would otherwise get delivered towards the user's account, is removed on entry to the campus network. Adoption of this approach has significant benefits to the efficiency of the email delivery process.