Inbox Placement Rate
Inbox placement rate is the percentage of successfully delivered emails that land in the recipient’s primary inbox rather than being filtered to the spam or junk folder or another tab.
It is a more meaningful deliverability metric than delivery rate alone, because an email can be technically delivered (accepted by the receiving server) while still never being seen by the recipient if it is routed directly to spam.
Inbox placement rate is determined by a combination of factors that inbox providers evaluate on every incoming message: sender reputation (the historical behaviour associated with the sending IP and domain), authentication (whether SPF, DKIM, and DMARC pass correctly), content signals (whether the email’s content and formatting patterns resemble spam), and engagement history (how recipients at that provider have interacted with previous emails from the same sender). Strong performance across all of these factors pushes emails toward the inbox; weaknesses in any of them increase the risk of spam placement.