Solo founders adding AI to cold outbound see a deliverability collapse around day 60-90 because AI lifts personalisation breadth at the same volume rather than personalisation depth at lower volume. The collapse is mechanical: AI-templated personalisation degrades recipient engagement, engagement decay triggers spam-classifier de-prioritisation, lower inbox rate produces more complaints, complaints trigger soft blocks. The defensible 2026 posture: 30-40 sends per inbox per day, named-specific first-paragraph personalisation, reply-rate KPI not open-rate, plus a documented EU GDPR Article 6(1)(f) Legitimate Interest Assessment for B2B founders in scope of e-Privacy Directive.

Five-tool comparison: Smartlead (mailbox rotation + warm-up), Instantly (warm-up community + community signals), Apollo (B2B database bundled), Lemlist (video/image personalisation lift), Amplemarket (AI persona-research depth). All five reproduce the 90-day decay pattern when volume runs above the per-inbox threshold. Receiving infrastructure (Google Workspace, Microsoft 365) reads engagement decay as automated outreach signal regardless of which tool sent the email. EU GDPR + e-Privacy posture is what most US-headquartered tools do not handle out of the box — country-specific carve-out interpretation matters. Pairs with the operator email-triage stack on the inbound side.