Simplicity and inexpensive nature of e-mail
has made it one of the most preferred mode of communication even
in business circles. Being the cheapest mode of communication -
most people today prefer e-mail over telephone or fax. Perhaps the
nearest rival to e-mail today is SMS - which has limited scope in
The rising popularity of e-mails has attracted a whole range of
scamsters, professional hackers, virus writers and mail order businesses
to send mass e-mails. According to one estimate, nearly half the
mails circulating through Internet today are spam !
Mail Blocking By Spam Filters
Latest survey result by filtering firm MessageLabs
reveals that unsolicited email messages or spam account for an astonishing
67.6% of the 841 million emails scanned during April' 2004 (source:
If half to two-third of all messages sent globally are unsolicited
- imagine the financial strain on individuals and corporates who
have to sift through this junk everyday. European firms are estimated
to have lost US Dollar 2.5 billion dealing with junk mail.
As a result - almost all ISPs use some kind of spam filter to counter
this menace. SpamAssassin is one such anti spam software - that
many ISPs around the world use.
Unfortunately, spam filters block legitimate e-mails also alongwith
spam. No anti-spam software can claim to block 100% spam or allow
100% legitimate mail to pass through. As a result, your legitimate
e-mail may get blocked by a spam filter without you or your recipient
ever knowing about it.
Deliberate Mail Deletion By Recipient
What makes an e-mail suspect in the eye of a spam
filter ? You should know that and make sure your legitimate e-mails
do not look like a spam. If it does - it will never reach recipient's
mailbox. Worse - neither you nor the recipient will ever know about
it as most spam filters do not inform the recipient about blocked
Even the recipient may delete the mail without reading, if it looks
like spam. Because of spam and e-mail-borne viruses - most people
these days check e-mails at server and download these only after
deleting suspect looking e-mails. The decision to delete an e-mail
is mostly based on quick look at its header - mainly subject. So,
if subject of your e-mail is a suspect - chances are it will end-up
in trash folder 'un-read'
How Spam Filters Work ?
It is important at this point to learn how a spam
filter works so that we can take precautionary measures to ensure
our e-mails do not get blocked by it. We shall take SpamAssassin
as an example
SpamAssassin works by "scoring" each e-mail message against a range
of tests designed to identify if that message is spam or not. A
wide number of tests are provided, including checks to see if the
sender and recipient address are valid, if the message dates are
valid, if the body contains any of a list of forbidden words, if
any of the sending servers are blacklisted, and so on. Each test
adds to a message's overall spam score; messages over a certain
user-defined threshold are treated as spam and can be either trashed
or marked with a special spam header.
In addition to these tests, SpamAssassin comes with a Bayes algorithm
which "learns" to recognize new spam on the basis of old spam messages.
This makes it possible for the software to automatically adapt and
identify spam even in the absence of specific header or body tests.
In next issue, we shall discuss specific elements
that make a legitimate e-mail spam suspect as also how to avoid
Happy and Productive Surfing
Dr. Amit K Chatterjee
- Newsletter on Business Opportunties from India and Abroad
Vol: 5, Issue 6
; September 16' 2004
Dr. Amit K. Chatterjee
(Amit worked in blue-chip Indian and MNCs for 15 years in various
capacities like Research and Information Analysis, Market Development,
MIS, R&D Information Systems etc. before starting his e-commerce
venture in 1997. The views expressed in this columns are of
his own. He may be reached at firstname.lastname@example.org