Amazing. Never. Problem. Wife. Success. Leave.

These are all common words that you might use in an email subject line without a second thought.

They also might be why the open rates in your email marketing campaign are so low.

As people’s tolerance of junk email has decreased and spam filter sophistication has increased, the list of spam filter trigger words has lengthened.

Not only could any sales-y word in the dictionary get you canned quicker than Spam™, but as email marketers have resorted to more general terminology for their subject lines, spam filters have kept pace.

There are already plenty of reasons your well-meaning email might be consigned to the digital gulag before it can be received: links to blacklisted websites, being sent from a blacklisted IP address, inconsistent “from” and “reply to” domains and addresses…

But let’s focus on the writing. What can you do as a writer to ensure your email gets through the barricade?

Below are some tips to help make sure your writing isn’t interfering with delivery of your emails.


Check subject line words for known triggers

Every internet service provider and email service filter has a list of “trigger words” that will get your email culled from the herd. The game is to write an engaging subject line while avoiding these trigger words.

My process for writing subject lines that capture the attention of readers (but not spam filters) goes like this:

  1. Familiarize myself with lists of known trigger words.
  2. Freely write 20-30 potential subject lines.
  3. Replace or eliminate words or phrases using known trigger words, or anything that sounds too sales-y. First of all, sounding sales-y is an almost sure way to get people to NOT open your email – but secondly, words or phrases with a promotional sense to them will almost certainly trigger spam filters.
  4. Check each word or phrase of the best subject lines against lists of known trigger words.

That last step may seem arduous, but the few minutes it takes to double check each word could be the difference between most of your emails getting through the filters, or none.

Which do you think will have a greater impact in the end?

A couple of tips:

  • Some people segment their email marketing lists by major domain name (,,, etc.) and check subject lines against the specific trigger words for each domain. This is probably unnecessary if you compile a comprehensive list of trigger words from various sources and make sure your subject line violates none of them.
  • DON’T get clever and try to get around filters by using special symbols to obfuscate trigger words, like “f^ree” or “prof!ts.” This just makes you look like a spammer.


Write subject lines the reader can’t ignore…

…because just as the reader opening the email depends on subject line engagement, future emails making it to their inbox depends on them opening the email this time around!

Email services like Gmail, with more than 1 billion active users, pay attention to which emails users open. If you’re an unknown sender and they don’t open your email, there’s a good chance your emails will be filtered out in the future.

I have no data on how quickly this decision is made by the filters or after how many no-opens, but the point is: write really engaging subject lines to make sure your email gets opened! And make sure to follow all other email marketing best practices so that nothing else interferes with that killer subject line being seen.

But with so many constraints on what words are allowed in a subject line, what do you have left to work with to craft an irresistible subject line?


Do you like green eggs and ham?

Due to its French and German influences, the English language happens to have a broader selection of nouns and verbs than many other languages. A good writer will find other words to get the point across.

And surprisingly, writers often work best under constraints like deadlines and word limitations that force them to be more creative.

Did you know that the writer known as Dr. Seuss took a bet that he couldn’t write a children’s book using only 50 words?

The result was a little ole’ book known as Green Eggs and Ham. Perhaps you’ve heard of it?

Besides, the spam filters can’t filter out everything – filtering services must temper security measures with the reality that if they filter too heavily, the emails recipients need and desire to read won’t make it through. They’ve left plenty of material to work with.

Remember, engaging subject lines are the most important part of an email – but knowing what NOT to say can be just as important as writing a surefire email-opener. Craft with care!