Email Subject Line Spam Score Checker

How a subject line racks up a heuristic risk score

The subject 'FREE!!! You won a prize - act NOW' scores 7 out of a rough risk scale, flagged for three separate issues: 'free' (the word triggers a +2 point flag), 'extra bangs' (multiple exclamation points, +2), and 'classic phrase' (phrases like 'you won' or 'act now' matching common spam-trigger language, +3).

Each flag is independent and additive -- this subject line hits three separate rules at once, which is why its score (7) is high relative to a subject line that might only trigger one or two of these patterns individually.

The scoring also checks for ALL-CAPS text (on subjects longer than 8 characters) and excessive length (over 60 characters), neither of which triggered here, but both of which would add further points to an already-risky subject line combining multiple red flags.

What this heuristic can and can't tell you

Heuristic only. Authentication, list quality, and HTML still decide the inbox. This checks only the subject line's text for word patterns statistically associated with spam filtering -- it says nothing about your sending domain's authentication (SPF, DKIM, DMARC), sender reputation, list engagement quality, or the email body's HTML structure, all of which weigh more heavily on actual inbox placement than subject-line wording alone.

A subject line can score 0 on this heuristic and still land in spam due to a poor sender reputation or unauthenticated domain, and conversely a subject line with a moderate score can still reach the inbox fine if the sending domain and list quality are strong.

These specific trigger words and phrases ('free', multiple exclamation points, urgency phrases like 'act now') are well-documented, long-standing spam-filter patterns, but modern filters also weigh many signals this simple text heuristic doesn't check at all.

Fixing a flagged subject line

Removing the exact trigger words and phrases (rewriting 'FREE!!! You won a prize - act NOW' to something like 'Your discount code is inside') addresses the text-level flags directly, though it won't fix deliverability problems rooted in authentication or sender reputation.

For the email body itself, similar spam-trigger patterns in the main content can compound subject-line risk -- review both together rather than optimizing the subject line in isolation.

Frequently Asked Questions (FAQ)