Email deliverability

Email deliverability describes whether a sent email successfully arrives in the recipient's inbox, as opposed to being rejected outright, bounced, or routed to a spam folder. It is a precondition for every other email metric: an email that never reaches the inbox cannot be opened or clicked, no matter how good email open rate or click-through rate look on emails that did get through.

Deliverability is shaped by sender reputation, built up over time from engagement and complaint rates, technical authentication such as SPF, DKIM, and DMARC records that prove an email genuinely comes from the domain it claims to, and list hygiene, meaning how clean and permission-based the recipient list is. Unlike open or click rate, deliverability problems often show up as silence rather than a visible failure: sends that appear to go out normally but quietly land in spam for a meaningful share of recipients.

Deliverability matters because it is invisible until it is measured deliberately, through inbox placement testing or by tracking bounce and complaint rates over time, and because it degrades gradually as list quality erodes, for example from buying lists or failing to remove chronically unengaged addresses, which is a matter of data quality as much as marketing practice. A single poorly targeted or purchased-list send can damage sender reputation for weeks afterward.