Definition
A prompt block list (also called a word block list) is a set of trigger terms and phrases that email filters, client-side rules and AI classifiers use to downgrade or block messages. Classic entries include aggressive sales language ("free", "guaranteed", "act now"), all-caps words, excessive exclamation marks, and spam-sounding patterns.
The list has changed as filtering has evolved. Modern inbox providers weigh reputation and engagement far more than individual words, so the block list matters less than it did a decade ago. But it still matters at the margins: heavy urgency language, fake scarcity and undifferentiated AI copy remain flags for both spam filters and increasingly cynical subscribers.
Common Block List Categories
- Overpromising — "guaranteed results", "make money fast"
- Fake urgency — "act now", "limited time" with no real deadline
- Spammy formatting — ALL CAPS, excessive punctuation, urgent emoji
- Money triggers — "free", "cash bonus", "no cost" used aggressively
What Actually Hurts Deliverability Now
- Low engagement (ignored, never opened mail)
- High complaint rates and spam marks
- Poor authentication (SPF, DKIM, DMARC failures)
- List hygiene issues — stale, purchased or trapped addresses
Related Terms
Related Glossary Terms
A/B Testing
A/B testing in email marketing is the practice of sending two variations of an email to a small sample of your list to determine which version performs better before sending the winner to the remaining subscribers.
Abandoned Cart Email
An abandoned cart email is an automated message sent to customers who added items to their online shopping cart but left without completing the purchase. It is one of the highest-converting email types in ecommerce.
Abuse Complaint
An abuse complaint is a report from a recipient who marks an email as spam, which negatively affects sender reputation and deliverability.
AI Content Detection
AI content detection refers to the growing ability of email clients, spam filters and consumers to identify machine-generated email copy. It matters for deliverability, trust and engagement in an era of mass-produced AI marketing email.
AI Email Summary
An AI email summary is a short, machine-generated overview of an email's key points, shown by Gmail, Outlook and Apple Mail before a recipient opens the message. It is reshaping how email marketers think about subject lines, preview text and open rates.
AI-Generated Content in Email
AI-generated content in email is copy, images, code or subject lines produced by artificial intelligence tools to speed up campaign production and testing.
Frequently Asked Questions
Rarely by themselves. Gmail's filters are engagement- and reputation-based. Trigger words matter most in low-reputation contexts or when combined with other spam signals.
Use it as a copywriting sanity check, not a straitjacket. Avoid the worst offenders, but prioritise relevance, authentication and list quality — they outweigh any individual word.
AI inboxes summarise and rank email rather than block words. Their emphasis on clarity means bloated, trigger-word-heavy copy summarises badly — another reason to write clean, specific email.