Spam Filters – How do they work?
What is a Spam Filter? A spam filter is a program that is used to detect unsolicited and unwanted e-mail and prevent those messages from getting to a user's inbox. A spam filter looks for certain criteria on which it bases judgments. These criteria can include specific words that may be inappropriate. The filter can also use an algorithm to determine the likelihood of a message being spam.
There are a variety of different spam filtering packages which vary in effectiveness. But they all have the potential to read a legitimate email and rate ii as a spam message. As part of the PLANNING RESULTS process, we look at ways to ensure that emails sent have the lowest possible spam rating.
Most anti-spam filters work by scoring email messages based on the email headers, subject and body text - some common triggers would include:
- The subject line starts with "free" or contains FREE in caps.
- The email contains the word "free" in certain phrases (free offer, free access etc.).
- Certain words like "guaranteed" in capitals.
- Words like "unsubscribe," "leave," and other list removal phrases.
- Using font sizes that are +2 or larger - or equally very small fonts.
- Minimize use of large fonts, coloured fonts and ALL CAPS
- Background in an HTML email that isn't white"
- Urge you to call now or claims you can be removed from the list.
- Phrases like 'what are you waiting for', 'while supplies last' etc.
- If your subject is something like "urgent assistance needed," your mail looks like the Nigerian business opportunity scam to the filter. Do not begin the subject with "urgent" or "very urgent" and follow with one of these words: confidential, assistance, business, attention, reply, response, help
- Use a specific, descriptive subject.
- Money back guarantee.
Here are some of the default SPAM triggers found in Outlook:
- From is blank
- Subject contains "advertisement"
- Body contains "money back "
- Body contains "cards accepted"
- Body contains "removal instructions"
- Body contains "extra income"
- Subject contains "!" AND Subject contains "$"
- Subject contains "!" AND Subject contains "free"
- Body contains ",000" AND Body contains "!!" AND Body contains "$"
- Body contains "for free?"
- Body contains "for free!"
- Body contains "Guarantee" AND (Body contains"satisfaction" OR Body contains "absolute")
- Body contains "more info " AND Body contains "visit "AND Body contains "$"
- Body contains "SPECIAL PROMOTION"
- Body contains "one-time mail"
- Subject contains "$"
- Body contains "$$"
- Body contains "order today"
- Body contains "order now!"
- Body contains "money-back guarantee"
- Body contains "100% satisfied"
- To contains friend@
- To contains "public@"
- To contains "success@"
- >From contains "sales@"
- >From contains "success."
- >From contains "success@"
- >From contains "mail@"
- >From contains "@public"
- >From contains "@savvy"
- >From contains "profits@"
- >From contains "hello@"
- Body contains " mlm"
- Body contains "@mlm"
- Body contains "///////////////"
- Body contains "check or money order"
It is not to say you cannot use these words - they are just likely to score worse than others and be 'more likely' that the email would be caught as spam.
You may ask - why tell people this - are you not just telling spammers how to avoid these. The answer is that they will already know - most spammers install anti-spam software and score their own messages to try and get them through spam filters!
On top of this many spam filters employ other techniques including blacklists and whitelists to help improve the accuracy of their filtering.
If you want to know more about spam filters and how they could effect your email communication please contact Henryk at PLANNING RESULTS.