Email Marketing: These 10 Phrases could get your Emails Consigned to the Spam Folder

Recent data shows that spam emails now comprise nearly 46% of all global email traffic in 2025, with experts projecting this could rise to 58 billion junk emails daily within the next four years. A new study by ZeroBounce analyzed publicly available email datasets from Kaggle to identify the words most commonly flagged as spam.

The research focused on words and phrases like “earn cash” and “no credit check,” which more than doubled the chance of landing in the spam folder. The analysis identified the most frequently flagged spam words, measured their prevalence in spam compared to legitimate emails (commonly referred to as “ham”), and categorized each based on the type of spam content in which it most commonly appears. The words are ranked by spam frequency, highlighting the likelihood of each word appearing in a harmful email.

You can access the full research findings by following this link.

The word that flags the email as spam the most is ‘viagra’, with the highest spam frequency. The word is 213% more likely to be in a spam email than in a regular one. The adult emails are also the most likely category of messages to be spam, with words like “viagra”, “xxx” and “adult” being immediately flagged as a sign of a harmful email.

“Click” ranks 2nd on the list of words that are flagged as spam the most, with a spam frequency of 735. It is often used by clickbait-spam emails, and the emails containing it have a 147% higher chance of being harmful. The ham frequency of emails containing ‘click’ is low at only 4.

“Cash” takes third place, with a spam frequency of 689. It is tied to the financial category of spam emails, which is the second most common. “Cash” is used more often in regular emails than ‘click”, but the ham rate for it is still low, at only 6.

“Winner” holds fourth position, getting a spam frequency of 652. Another word used in clickbait spam, it has a lower spam-to-ham ratio than “click” at 81.5.

“Urgent” is fifth in the ranking of the words that are most commonly flagged as spam, with a spam frequency of 603. While flagged as spam, it is also used for actual critical messages, so its spam-to-ham rate is lower, at only 67.

“Offer” takes sixth place, with a spam frequency of 591. Often used in marketing emails, it has the third-lowest spam-to-ham rate at 53.7, showing that many marketers still use it despite the word being flagged as spam.

In seventh place is “sex”, getting a spam frequency of 580. Another common word used in adult-themed spam, it has the lowest ham frequency in the ranking, showing that it’s almost exclusively used in harmful emails and should be avoided by general users.

“Money” follows closely with eighth place and a frequency of 577 in spam emails. The word has the second-highest ham frequency of 11, showing that it is often used in regular emails despite the risk of being flagged.

“Limited” is ninth, getting a spam frequency of 565. Similar to “urgent”, it appears often in “urgency” spam emails, and has a 56% higher chance of containing harmful or useless information.

“Deal” rounds up the ranking of the words most commonly flagged as spam, with a spam frequency of 554. The word has the highest ham frequency of 15, appearing in non-malicious emails most often among the top 10 words in the ranking. “Deal” is most often used in marketing messages, highlighting the need to approach promotion with more careful choice of words.

Vlad Cristescu, Head of Cybersecurity at ZeroBounce, commented on the study and broke down the misunderstood signals that trip up deliverability algorithms, even for legitimate businesses: