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Dealing with Spam

This page describes some of the facilities available to deal with the increasing menace of spam (unsolicited commercial email). Please read the EUCS's general guidance when dealing with spam.

These instructions describe how to set up spam filtering using the web interface to mail.inf. You can use this method to enable spam filtering even if you don't use the web interface as your regular mail reader, and you can continue to read your mail with your regular email program once filtering is enabled. If you would like to set up spam filtering from within your usual email program (i.e. not using the technique detailed below), then see the EUCS documentation on client-based filtering on the SpamAssassin page. We strongly recommend that you use the server-based filtering mechanism described below. Remember you can then continue to read your mail using your regular email client.

Incoming mail is being passed through a tool called SpamAssassin. This tool uses various rules, and a self-learning mechanism, to decide whether a piece of mail is likely to be spam or not. It then rewrites the header of the message and inserts a score (varying from 0 up to 40 — in practice scores higher than 15 are almost certainly spam) on the likelihood of the message being spam. The higher the number the more likely it is that the message is spam. You can use this information in a filtering rule to separate out likely spam to another folder, which can then be more easily processed by yourself and deleted if it is spam. Because the score is just a heuristic, and only you can decide ultimately whether a message is spam or not, we do not recommend automatic deletion of messages.

There are two conditions where mail is not scanned for spam.

1. If the mail is passed to the mail relay from a machine from within ed.ac.uk. For example, if you are forwarding mail from a mail address you have at some other .ed.ac.uk department/school and they are accepting external mail connections directly.
2. For operational reasons (performance and stability), mail larger than 48 kilobytes in size is not scanned.

Setup a spam filtering rule

To setup a spam filtering rule, first logon to the web mail interface at mail.inf.ed.ac.uk, then click on Filters from the menu at the top of the screen. Near the top right of the screen there is a button marked Insert spam filter. Click on this and a new rule box appears (see Figure 1).

Figure 1. A new spam filter rule

• Next you need to set the score at which point the rule will trigger and treat the mail as spam. You will need to find a score which suits the type of mail you get. You can easily adjust this up and down until you get a good balance between trapping most spam and not mis-directing real mail. We have set the default to be 4 as that seems to work for most types of mail.

• Now you need to specify a mailbox in which to save the filtered mail. Enter the name of a mail folder in the box provided.

• If you want to bypass the spam scoring mechanism altogether, because you know that you will never receive spam from a particular mail domain e.g. ed.ac.uk, then you can optionally specify a list of such mail domains in the whitelist box provided. This provides a list of exceptions to the spam filtering rule. You should list each mail domain on a line by itself. The mail domain is the part on the right hand side of the address after the @ symbol. Please note that by specifying a domain you also include any sub-domain e.g. ed.ac.uk includes sms.ed.ac.uk. Note that if you have incorrectly formated the mail domains e.g. used a disallowed character, or not put one per line, you will not be able to enable the rule until you correct it.

• Now press the Enable this rule button to activate the spam filter. The pink back ground will turn green to show it's been enabled.

• Please remember to check and clear out your spam folder from regularly. This will save disk space, and it is likely that some legitimate mail will end up there too.

If you want to find out why a particular message was caught by your spam filter, then go to the message view screen and click on the Message Source button. In the mail header you will see a line beginning with X-Spam-Level. You need to count the number of asterisks to find out the SpamAssassin score of that message. You can use this to adjust the score you set above. Alternatively, you can use whatever method the mail client you normally use to read mail provides for inspecting the full mail headers of messages; please refer to the documentation provided for each supported mail client.

Acknowledgements

This page is a reworked version of an existing EUCS web page, but modified for Informatics users.