Step 4/5. Form captures email. The submitTo carries fresh utm_source=email — when the visitor 'submits' the form, they land on the next step with email as the new tagged source. This simulates a real-world re-engagement click via an email link. Tests how the tracker resolves a brand-new tagged click mid-session: does it open a new attribution window (last-click) or stick with the original paid source (sticky-session)?
Conversion tracked: lead (ref: mt-opt-in)0