What Is Deliverability?

Three authentication records, SPF, DKIM, and DMARC, are the baseline technical layer inbox providers check before deciding whether a sending domain looks legitimate. Missing or misconfigured records are one of the fastest ways a cold-email campaign gets routed straight to spam regardless of how good the copy is.

Reputation is the harder, slower-moving layer on top of that. A domain that sends high volume to a cold, unverified list, or gets marked as spam by enough recipients, degrades over time, which is the whole reason email warmup exists as a separate discipline before a domain is trusted with real outbound volume.

The category's newest deliverability risk is AI-run email outreach specifically. Secondary analysis of AI SDR tool performance found deliverability commonly collapsing from over 90% inbox placement down to under 60% by week four of a campaign, with reply rates falling from 4% to 6% down to 0.5% to 1.5%, and cost-per-meeting rising from roughly $35 to $150 to $300 over that same stretch, a pattern attributed to unmonitored volume and list quality drifting without a human catching it. That data is modeled, not officially disclosed by the vendors involved, so treat the precise figures as directional rather than exact.