Deliverability

Deliverability is the catch-all term for the discipline of getting email into the recipient's primary inbox rather than the spam folder, the Promotions tab, or outright rejection. It's distinct from delivery rate (which measures whether the email reached any folder at all) — deliverability is about which folder.

Deliverability outcomes are driven by sender reputation, authentication (SPF/DKIM/DMARC), content signals, recipient engagement, and infrastructure (sending IP warmth, domain age). Most deliverability problems trace back to one of three causes: bad list hygiene (high bounces, low engagement), authentication misconfiguration, or content that triggers spam filters (excessive caps, link-heavy bodies, suspicious link targets).

Deliverability isn't a one-time setup; it's a continuous discipline. Engagement metrics directly feed sender reputation, which directly feeds future deliverability. Cold sending to a stale list is the classic deliverability suicide: low engagement signals to ISPs that you're a spammer, which causes more mail to be filtered, which lowers engagement further.