This page was last updated: 2/6/2015 11:43:53 AM
I'm receiving SPAM email in my Outlook inbox. How are these
messages getting through?
Q7: I'm receiving SPAM email in my Outlook inbox. How are these
messages getting through? Why doesn't our anti-spam system stop these messages?
Why are legitimate messages sometimes quarantined as SPAM?
A: Spam email is a problem facing all organizations (schools,
businesses, government) that use Internet email. CWSL is not being singled out,
nor are we sitting idly by allowing massive amounts of spam email to clog our
email system. The CWSL email system agressively filters unwanted email by
employing multiple levels of anti-spam filtering to the incoming email stream.
First, our incoming email is filtered by a Barracuda Networks Cloud service.
This blocks a percentage of spam and email viruses before it even reaches
our network. Next, as email enters our network, it is analyzed by an
on-site email security appliance, also by Barracuda Networks. It also blocks
email that has an extremely high spam index. If it identifies an email as being
"possibly" spam, it allows the message to come through, but tags the subject
with [possible spam]. The final level of anti-spam filtering occurs
when your Outlook email software reads your inbox on our Exchange server.
Any messages that are deemed spam by Outlook's Junk E-mail filter are
immediately moved into your Junk E-mail folder.
Important Note: the end user (you!) does not have the
ability to whitelist email messages that are blocked by either of the Barracuda
filtering layers. It's very rare that this occurs. If it does, please contact
HelpDesk and we'll address this for you. However, if messages are ending
up in your Outlook Junk E-mail folder, you can "whitelist" these messages
yourself. Just right-click on the message, select Junk, then
select one of the "add to Safe Senders" options.
These various filtering layers work to eliminate the vast majority
of spam entering our network. For example, the Barracuda services
filters over 80% of the incoming email stream as spam! Let me repeat that, because
it's worth repeating. Around 80% of the email sent to cwsl.edu addresses from
the Internet is spam, and is blocked before it ever reaches our email server or
So why isn't it able to stop all spam messages, you may ask. Why is a message
that is so obviously spam (to the human eye) allowed to get through a spam filter? There are several reasons for this
(and to answer this we have to put our geek hats on for a bit).
First, keep in mind that it is relatively easy for the cognitive abilities of
(most) humans to quickly identify a message as spam. It is simply not feasible,
though, to have a human scan every message coming into a network (our network,
for example, receives over ten thousand messages daily). But for a computer
algorithm, it's not so simple to positively identify spam. Computer algorithms
can't look at a message the way a human does and simply "know" that a message is
spam. It has to perform various tests to determine the nature of the
message...and it's doing this on perhaps hundreds, if not thousands, of messages per minute.
Therefore, even the most effective anti-spam systems on the market are able to
correctly identify about 95% of the incoming spam. Some spam inevitably gets
through. For this very same reason, the algorithm sometimes will mistakenly
identify a legitimate message as spam. This doesn't happen often, but it does
Another reason that spam is sometimes able to get through is that the
creators of spam are always working to find new ways to circumvent anti-spam
systems. It is a never-ending cat-and-mouse game. There simply is no 100%
effective means of stopping spam. There is no "silver bullet" device that is
capable of stopping all spam email. Spam is a global problem plaguing every
organization that uses email. Fancy spam filtering appliances and email client
software, working together, can put a sizeable dent in the problem, but some
spam email will inevitably get through. At that point, the last line of defense
is the "Delete" key.
Some key points of spam filtering to remember:
- Spam is a global problem facing all organizations using Internet email.
- Spam detection devices can stop the majority of spam, but not all of it.
- Occasionally, legitimate messages will be incorrectly identified as spam.
- The vast majority of spam entering the CWSL network is either blocked
completely or quarantined
before you ever see it. The little bit of spam that does come through is a
trickle compared to that which was sent to you and stopped by the spam
- If you receive spam messages in your inbox, please do not feel it is
necessary to report this to us. Simply delete the message.