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The 5 best words for subject lines (and 5 to avoid)

With so many emails per day and so little time to connect, subject lines are crucial.

While there are no “magic” words for subject lines, there are a few keywords that have shown great success in increasing open rates (how many people on an email list open a particular email) and engagement rates (the number of unique email recipients who opened an email or clicked on a link in an email over time).

Here are the top performers:

  1. Alert: Emails with the word “alert” in their subject lines have a higher likelihood of being opened and clicked through, according to a study by Adestra.
  2. Bulletin: Emails with the word “bulletin” also have a higher likelihood of being opened and clicked through.
  3. Daily or Weekly: Date-specific keywords can be highly effective, but only to an extent. The word “daily” has a slightly higher open rate, as does the word “weekly,” but “monthly” is not as strong overall.
  4. News: Content pieces that have the word “news” in the subject line generally perform well.
  5. Names: In some cases, personalising a subject line can help with open rates. For example, a Sheriff’s department (and Granicus client) discovered that when their Sheriff or officer’s name was included in the subject line, their open rates doubled.

On the other hand, there are number of keywords that can be detrimental to open and engagement rates, including:

  1. Free: Near the top of the list of words to avoid for email subject lines is “free” due to overuse. It can also harm a sender’s reputation.
  2. $$$: Symbols and emojis are usually triggers for SPAM filters.
  3. Guaranteed: Naturally, the word “guaranteed” can bring on a level of scepticism by a reader, and are quickly dismissed or deleted.
  4. Report: While “bulletin” has strong results in terms of open and engagement rates, “report” does not fare well. If you are sending a report, whitepaper or journal to readers, try using descriptive words instead.
  5. Earn: The word “earn” can be associated with money-making plans, which readers are not interested in if they don’t know you.

There are no “perfect” words for increasing open or engagement rates, but there are other considerations that can contribute to your success:

Be relevant: Make your subject line relevant to what your audience wants to hear from you.
Consider timing: Capitalizing on a news hook or something timely can have a great impact on open and engagement rates.
Add in a “call to action”: When referencing a call to action in your subject line, be clear and simple. Use verbs like “Register,” “Meet up” or “Tell us”
Experiment: By A/B testing different subject lines or calls to action, such as a button or an image instead of hyperlinked text, to see if you can drive more click-throughs.

Content marketing guide UK

Do you have examples of words that have worked well for your organisation’s email campaigns? Let us know at