Frequency Saturation

E4 — distribution of contacts by emails-received-in-window × their engagement, so an operator can see where MORE email stops helping.

'Emails received' is counted from per-recipient delivered events (one per recipient per send) over the window; each contact's open/click rate is computed from their own events in the same window. Contacts are bucketed (0,1,2,3-5,6-10,11+) and the per-bucket average open/click rates are the headline. recommended_cap is the bucket beyond which average engagement DROPS materially from its running peak — a grounded heuristic, not a model.