What subject line mistakes trigger spam filters?

Modern spam filters rarely block emails based on subject lines alone-context matters far more than keywords. However, certain patterns can contribute to negative scoring when combined with other signals from untrusted senders.

Patterns that raise flags: Deceptive prefixes (fake \"RE:\" or \"FWD:\" on marketing mail), excessive punctuation (!!!, ???, $$), ALL CAPS SHOUTING, deliberate misspellings to evade filters (\"Fr33\" instead of \"Free\"), and symbol stuffing (★★★URGENT★★★). These aren't automatic triggers but signal amateur or deceptive intent.

The real subject line mistake is dishonesty. A subject that doesn't match body content generates complaints. Bait-and-switch tactics might boost opens once but destroy trust and reputation. Filters learn from recipient behavior. If uyour subjects consistently disappoint, your emails get filtered. Write honest, relevant subjects and let your reputation do the heavy lifting.