Spam Filter Triggers

Modern filters are classifiers trained on behaviour, not keyword lists. The old "never write the word free" advice is mostly folklore, and the sites that score your email out of ten are matching against rules that stopped being decisive years ago.

What actually decides placement, in order:

1. Authentication and domain reputation     ~60% of the outcome
2. Recipient behaviour — replies, deletions, complaints
3. List quality — bounces, traps, dormant addresses
4. Content and structure                    ~10% of the outcome

So if mail is going to spam, check the first three before rewriting the copy. Content is the smallest lever and the one people reach for first. See email-deliverability for the rest.

That said, content does matter at the margin, and the margin is where a lot of cold email sits.

The things that genuinely hurt