What Is a Spam Score?
A spam score is a single number, usually between 0 and 1, that combines several independent signals about a submission into one verdict. A threshold turns that number into a decision: deliver it, hold it for review, or reject it outright.
Scoring exists because no single signal is trustworthy alone. A message containing a link is not spam. A short message is not spam. A message from a free email address is not spam. A two-word message containing three links from an address at a domain registered yesterday almost certainly is. Each signal contributes weight, and the total is what gets acted on.
The interesting decision is not the scoring, it is what the threshold does. Set it high and junk reaches the inbox. Set it low and a real enquiry gets filed as spam, which costs far more than the junk it prevented. Most systems that feel broken are badly calibrated rather than badly built.
Scores drift as senders change tactics, which is why a filter that is never revisited slowly gets worse. The useful habit is to look at what landed near the threshold rather than what scored 0.9.
In WebForms
WebForms quarantines at 0.6 by default rather than deleting, and certain content is rejected outright regardless of score. The threshold is configurable per form, because a job application form and a support form have very different costs for a wrong call.