Content, trigger words and subject lines


There’s been quite a bit of traffic on twitter this afternoon about a recent blog post by Hubspot identifying trigger words senders should avoid in an email subject line. A number of email experts are assuring the world that content doesn’t matter and are arguing on twitter and in the post comments that no one will block an email because those words are in the subject line.
As usually, I think everyone else is a little bit right and a little bit wrong.
The words and phrases posted by Hubspot are pulled out of the Spamassassin rule set. Using those words or exact phrases will cause a spam score to go up, sometimes by a little (0.5 points) and sometimes by a lot (3+ points). Most spamassassin installations consider anything with more than 5 points to be spam so a 3 point score for a subject line may cause mail to be filtered.
The folks who are outraged at the blog post, though, don’t seem to have read the article very closely. Hubspot doesn’t actually say that using trigger words will get mail blocked. What they say is a lot more reasonable than that.

Trigger words are known to cause problems and increase the chances of your email getting caught in a SPAM trap. By avoiding these words in your email subject lines, you can dramatically increase your chances of getting beyond SPAM filters.

OK, so I’m not sure about the “dramatic” part, as some of the words they list as triggers in the subject lines will also trigger scores when used in the body of the message. But the gist of the Hubspot post is not wrong. If you use too many words and phrases used by spammers, then your mail is going to be difficult to distinguish from spam. I don’t think this is actually controversial (although I’ve been known to be wrong…)
But some of the comments on the post go too far in the other direction and totally misrepresent reality.

Content filtering hasn’t been a big component of spam filtering algorithms for nearly a decade.

This is blatantly and demonstrably untrue. Naive content filtering hasn’t been a big component for nearly a decade, but content filtering is where filtering is going. IP based filtering is good for some things but content filtering allows for much finer grained sorting and filtering. I think content filtering is where the industry is going. Too many spammers have created too many ways to avoid and subvert IP based filters for them to be the full solution to protecting users.
Content matters, don’t think it doesn’t. But don’t let word lists like the above frighten you off from crafting good subject lines.

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  • Good post.
    I agree with you that content filtering is still playing a major part in most spam filters. In some cases the use of a single word/phrase may lift the spam score above the threshold and will the see email being blocked.
    But I seriously wonder where they god that list from. I mean ‘get’, ‘home’, ‘order’, ‘form’, ‘call, ‘now’, …

  • The wrong things that people “know” about spam filtering are just amazing. I’ve met people who are sure that nobody’s used DNSBLs for a decade.

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