How is inbox placement different from delivery rate?

Delivery rate measures whether the receiving server accepted your message during the SMTP transaction. A 98% delivery rate means 98% of messages were not rejected or bounced.

Inbox placement measures where those accepted messages actually land. You can have 100% delivery and 50% spam folder placement. The server took your mail but put half of it where no one looks.

ESPs typically report delivery rates because that is what they can measure directly. Placement requires seed testing, panel data, or sophisticated monitoring to detect.

Delivery is permission to enter the harbor. Placement determines whether you dock at the main terminal or get anchored in quarantine.