What we do...
IT Services is often asked what we do to combat the ever-increasing volume
of junk or spam email sent to college email accounts. Currently, all incoming
email is subject to the following procedures:
- Messages are subject to a 61 second delay - many spam sources will 'give
up' trying to deliver mail during this period.
- A message will only be delivered if it appears that a reply could be sent
to it. This avoids the (common) case where a spammer sends a message from
a completely bogus email address.
- Each message is assessed and 'scored' for the likelyhood of it being spam
using a system called SpamAssassin. The more points the message scores, the
higher the probability that it is spam.
* If a message scores 10 or more points, it is rejected outright and will
not reach the intended recipient's mailbox. Trials have shown that this action
reduces the number of spam messages reaching staff mailboxes by about 82%
and it is extremely unlikely that legitimate mail will be mistakenly rejected
(if you have evidence of this happening, please report it to email@example.com).
* If a message scores between 5 and 10 points, we add several
headers to it, including:
and alongside this header will be the word 'Possibly' (scores of 5 and
above) or 'Probably' (7.5 and above).
The addition of this Header allows you to set your own filters either on
the IMAP server or in your local mail client, to redirect such message to
a 'junk' folder(s). See below for details of how to set up filters.
Separating the spam in this way makes it much easier to deal with and the
junk folder can be checked and cleared periodically. Note that, as false positives
are possible, you are not encouraged automatically to delete mail messages
on the basis of the X-QM-Spam-Warning header.
If you want to see the added headers in your email messages, you will need
to use an option to display full headers
in your mail program although this is not necessary for filters to work.
See this guide
to interpreting mail headers.
What you can do...
Set up a personal filter on the central mail server.
If you use the IMAP mail protocol to read your mail, it is possible to set
up filters (Rules) on the mail server itself. This means that the filters
will be applied to your inbox before you access it and will therefore be effective
from wherever you read your mail and whichever client you use.
- To set up a simple rule to move any mail with a spamassassin score over
5.0 into a junk folder, follow these
- To set up more sophisticated rules using the X-QM-Spam-Warning header
or actual spamassassin scores, use the New Rule feature
Most email clients allow users to set up filters or rules to deal with messages
automatically. The filtering tools of the common email clients can be
found as detailed below (with thanks to the authors of external links):
Mozilla Thunderbird: Tools
> Message Filters (see also Junk control features in Thunderbird
(PC version 5.1): Tools
(Mac version 5.0): Special
Pegasus: Tools > Mail
Microsoft Outlook: Tools
> Rules Wizard
Micosoft Outlook Express
(PC version 5): Tools
> Message Rules (works for POP accounts only)
(Mac version 5.02): Tools
> Rules (also >Junk Mail Filter)
Apple Mail (MacOS X): Mail
> Preferences > Rules and Mail
> Preferences > Junk Mail
> Mail Management > Filters
All of these except Outlook Express and Webmail will allow you to filter
by some means, on the X-QM-Spam-Warning header. A search on the Internet may
provide other utilities that will enable filtering on customised headers.
You may also want to set up rules/filters to filter out messages containing
certain keywords of your choosing.
Remember that setting filters in your local mail client will only be effective
when you use that particular installation of the client on that particular
PC to read your mail. Also, it is safer to redirect filtered messages to a
junk folder for quick checking before deletion rather than deleting automatically.
Removal of 'qmw.ac.uk' aliases
Many instances of spam arrive via old style qmw.ac.uk addresses which may
also be used as spoof return-addresses by spammers, resulting in even more
unwanted mail in the form of undelivered spam.
If you still have an old style qmw alias for your email address and are sure
that you no longer receive any legitimate mail (check that any mailing lists
you subscribe to don't use the qmw version), you can send a message to:
requesting that it be removed from your mail registration details.
Turning off automatic display of content
Some email clients can automatically display a message's content in a "preview"
pane before you open the message in its own window. To prevent the unintended
display of potentially offensive messages or images, it may be possible
to configure your client not to show a message's content before you explicitly
open it. For example, in the following clients, uncheck these options:
Eudora: Tools > Options >
Viewing Mail > Preview Pane
Microsoft Outlook Express: Tools > Options
> Read > Automatically download
message and/or View > Layout >
Show preview pane
Microsoft Outlook: View > Preview pane
and View > Autopreview
In Thunderbird you can block the appearance of remote images:
Tools > Options > Privacy > General > Block loading of remote
Reporting Illegal Content
If you receive email containing what you believe to be illegal content,
you can report any web addresses (URLs) contained in the message to the
following web site:
What you shouldn't do...
Together the above measures can significantly reduce the amount of spam you
receive but unfortunately they will not eliminate it altogether. For messages
that do get through the advice is:
- Never reply to junk mail even if it says that doing so will remove your
name from a list - this will most likely just confirm that your email address
is a good target for further spam, or, the sender address could be fabricated
or falsified so you could just be targetting some other completely innocent
- Don't waste time on it - just delete it.