Email Deliverability
The percentage of emails that actually reach the inbox (not spam, not bounced).
Email deliverability is the rate at which sent emails successfully reach recipients' primary inboxes rather than spam folders or bouncing. Deliverability depends on sender reputation, authentication (SPF, DKIM, DMARC), list quality, and engagement metrics.
Context
A sender with poor authentication (missing or invalid DMARC, SPF, DKIM) will see deliverability rates drop to 50–70%. Proper authentication plus a clean engaged list typically achieves 95%+ inbox placement.
Engagement is the single strongest deliverability signal. Mailbox providers like Gmail watch open rates, click rates, and user actions (marking as spam, replying). Low engagement from a previously-clean list will tank deliverability within weeks.
A brand with 200K subscribers sending weekly campaigns went from 95% inbox placement to 71% within 6 weeks of acquiring a list via a promotional giveaway. The giveaway audience was low-engagement, which taught Gmail the sender's content wasn't wanted, which applied to the whole list.
Deliverability is measured per-domain, not per-ESP. Switching email service providers doesn't fix a bad domain reputation. Warming a new sending subdomain from scratch takes 4–8 weeks.