Personalization
Tailoring email content to the individual subscriber — beyond {{firstName}}, the meaningful kind uses behavior and segment data.
Personalization in email is the practice of tailoring content to the individual subscriber. The shallow version is name interpolation ({{firstName}}); the meaningful version uses behavioral and segment data — purchase history, last-viewed product, account tier, geography, lifecycle stage.
Shallow personalization is often worse than no personalization. A "{{firstName}}, your offer is here!" subject line where {{firstName}} is missing or wrong reads as automated and erodes trust. Best practice: never use {{firstName}} in subject lines; in body copy, only when the missing-data fallback is graceful ("Hi" instead of "Hi there,").
Behavioral personalization is where the conversion lift lives. Pulling the user's recently-viewed product into a browse-abandon email, surfacing their actual usage data in a SaaS engagement email, or naming a specific past purchase in a winback email — these are 5–20% conversion-rate lifts, not 1% lifts. The investment is in the data pipeline, not the email itself.