Why it matters
Opt-in source predicts list quality. POS opt-ins, loyalty enrollments, and e-commerce checkboxes carry different engagement profiles — and different compliance posture. Tracking source from day one makes everything easier.
How it affects messaging performance
High-quality opt-ins drive open rates, click-through, and revenue per send. Low-quality or fuzzy opt-ins drive complaints, opt-outs, and carrier scrutiny that affects every subsequent campaign.