Ask which part of delivery is actually measured
Technical acceptance by a server is different from placement in an inbox and different again from a person reading or replying. Opens can be affected by privacy features and automated fetching. A high open rate should not be treated as reliable proof of human engagement.
Inspect SPF, DKIM, DMARC where required, domain alignment, sending behavior, complaint monitoring and unsubscribe handling against current provider rules. Requirements vary by volume and recipient type. Ask who owns domains and mailboxes, what happens after a problem and how the client can inspect the evidence. Avoid a fixed safe-volume claim without context.
| Decision | Evidence to use | What changes next |
|---|---|---|
| Configuration | Authentication and identity aligned with provider requirements | Repair setup before interpreting campaign results |
| Monitoring | Destination-specific failures, complaints and suppression | Respond to problems rather than hide them in averages |
| Commercial outcome | Relevant replies and accepted opportunities by cohort | Assess usefulness separately from technical delivery |
Work through the decision
Illustrative proposal: an agency promises a 95% inbox rate but provides only a server-delivered count and an open-rate dashboard. Ask how inbox placement was tested and whether the sample represents your destinations. The supplied evidence may support delivery, not the stronger claim.
Next inspect an unsubscribe and a failed-delivery path using controlled records. If suppression does not propagate or failures keep being retried without review, the system is not ready merely because authentication passes. Treat warmup or tool-specific scores as inputs, not guarantees.
A proprietary score replaces destination evidence
A tool score can be useful but may not describe your actual recipient mix. Ask for method, sample and limitations. Do not turn an estimated score into a universal inbox or revenue guarantee.
A concrete next step
Request the method behind the strongest deliverability claim and a controlled failure/suppression demonstration. Keep unsupported promises out of the commercial comparison.
Sources and research notes
- Google: Email sender guidelinesMailbox-provider requirements
- FTC: CAN-SPAM business guideRegulator guidance; US scope
Primary sources reviewed October 6, 2026. The operating recommendations and worked scenarios are Daavid’s analysis. Illustrative numbers are assumptions, not measured client results. Company marks identify sources and prior experience; they do not imply a customer relationship or endorsement.
Schematic