It can be annoying to carefully craft an email and send it out to folks only to have it end up in their spam filter. There aren’t hard and fast rules for avoiding this, but knowing how spam filters operate can give you an idea how to keep your emails from landing in junk folders.

Spam filters “read” emails and each word is assigned a score based on how spam-like it sounds. “Viagra” for example gets a high score while another word such as “similar” receives a low one. The filter then calculates a spam score: the ratio of words with a high score to those with a low score. If the spam score is too high the email is treated as spam.

To make it more complicated, the spam filter “learns” based on words in email people mark as spam. So if for example I got spammed with a bunch of clothing ads and marked them as junk, another email about a clothing swap might get marked as junk. A decent rule of thumb is to avoid sex, money, “Great Offers!” and words related to those topics or that sound like solicitation. Often spam filters try to filter out abusive emails as well so racial and gender topics can be dangerous as well. If you do need to put these topics in an email make sure the email has plenty of innocuous text as well.

All caps (which people interpret as shouting anyway) is another bad idea. has some additional tips, such as avoiding pre-generated text, lots of hyperlinks, HTML codes, and graphics. You may also wish to check out the book Fighting Spam For Dummies. It’s written by a ITS staffer, but it’s been out for a few years and the specific software suggestions are out of date. (If you do get it, be sure to come by ITS to get it signed!)

Do you have tips or a tried and true method of avoiding the junk folder? We’d love to hear about it — just comment on this blog post.

About the Author
James Curran