How spam filters actually use trigger words
Modern filters at Gmail and Microsoft do not block an email because it contains the word free. They score hundreds of signals together: sender reputation, authentication, engagement history, link domains, formatting and, yes, vocabulary. Trigger words matter because they correlate with the mail people mark as spam, so they nudge the score in the wrong direction.
For cold email the bigger problem is often the reader, not the filter. Copy that sounds like a promotion gets deleted or reported, and every report trains the mailbox provider to route your next message to spam. This checker catches the vocabulary and formatting patterns that make a one-to-one email look like a campaign.
The six categories we check
- Urgency and pressure: act now, limited time, last chance. These push the reader instead of respecting their time.
- Money and financial: free, discount, make money, $ amounts. Classic promotional vocabulary that also draws phishing filters.
- Shady and manipulative: this is not spam, you have been selected, verify your account. The heaviest weighting, since these mirror phishing and scam templates.
- Over-promising: guaranteed, revolutionary, 10x, best in class. Claims that a sceptical buyer discounts and a filter flags.
- Salesy and cliche: I hope this finds you well, just checking in, leverage, seamless. Not dangerous on their own, but they mark the email as templated.
- Unnatural formatting: !!!, ALL CAPS, unsubscribe footers, link shorteners, fake Re: prefixes. Structural signals that a human wrote in a hurry or a tool wrote at scale.
Weighting reflects how strongly each category correlates with spam complaints. A single salesy cliche costs almost nothing; a phrase from the shady category costs a lot, especially in the subject line where it is counted twice.
Rewriting a flagged cold email
Start from the highest-weighted category and work down. Replace claims with specifics: instead of guaranteed results, describe what a similar customer did and how long it took. Instead of limited time offer, state the real reason for the timing, such as a quarter ending or a hiring push you noticed.
Before:
Don't miss out! Our revolutionary platform is 100% guaranteed to 10x your pipeline. Click here for a FREE demo!!!
After:
Saw you're hiring two SDRs. Teams at that stage usually lose a week per rep on mailbox setup. We handle domains, inboxes and DNS in an afternoon. Worth a 15 minute look?Keep the body between 50 and 125 words, use one link at most (none is better on a first touch), and close with a real name. If the sending domain is new, warm it up before sending anything; even perfect copy cannot rescue a domain with no reputation. InboxOne provisions domains and mailboxes with SPF, DKIM and DMARC already in place so the copy is the only variable left.
What this checker cannot tell you
The score is about copy. It does not test your sender reputation, authentication records, sending volume or the health of your IP, all of which matter more than any single word. A clean score here plus a failed DMARC record still lands in spam.
- Run the deliverability checker on the sending domain to confirm SPF, DKIM and DMARC.
- Send a seed test to your own Gmail and Outlook accounts before a campaign.
- Watch reply and complaint rates per mailbox; pull a mailbox out of rotation the moment complaints rise.
