A client recently complained to me that legitimate email to him was being flagged as spam. After a quick review of the email, it was pretty obvious why.
Spam filters use a variety of tools to identify spam. One of these is to analyze an incoming email to see if it contains typical spammer techniques. The filter gives a score to each technique found, which adds up to a cumulative score for the message. Your ISP or webmaster has the ability to set a threshold at the server - any message with a score above that threshold will be marked as spam.
So, what do filters look for? Here are a few common items with the approximate score (using our filter software) for each:
1. Incorrect HTML syntax. This can include unbalanced tags, missing tags, or the use of HTML tags that do not exist. (Score up to 1.5)
2. Yelling. That is, text in all uppercase. (Score of 0.1 per line)
3. Yelling in the subject line of the message. (Score of 0.6)
4. The words "As seen" in the subject line. (Score 2.5)
5. The words "click here" or "click below" in the message body. (Score 0.1 - 0.5)
6. Images with 200-400 bytes of words, or large images. (Score up to 1.4)
7. The message claims that "you provided" something. (Score 2.7)
8. Messages with the sent date after the received date. (Score up to 2.6 depending on time difference)
9. Subject contains the word "free". (Score 1.7)
10. Use of excessive HTML in the body of the message. (Score up to 1.5)
Obviously, using a poorly designed email template (those designed in MS Word and saved as HTML are the worst), capitalizing your text, including large images (for example, your company's logo as a part of your email signature without resizing it), and a few poorly chosen words or phrases can push the score for an email well beyond a score of 5.0. This was the case in my client's email - the sender was oblivious to fact that his email (a quote to do business) was breaking all of the rules.
A well designed piece of spam can stay below a score of 2 or 3. A poorly designed piece of spam (for example, those pretending to be from Fifth Third Bank) can generate a score of 9 or above.
The threshold that your ISP sets for spam can make the difference between your email getting through to its intended recipient, or being deleted as spam.
If you plan to use an email template, send large images, or use HTML in your messages, you may want to test your email first before using it. A poorly crafted email, combined with a few poor word choices could have a significant impact on your business.
