Deliverability
Whether mail is accepted and where it is placed — inbox, promotions, spam, or rejected.
Definition
Deliverability is the outcome of authentication, reputation, warmup, and content decisions as judged by mailbox providers.
Why it matters
Explain why messages reach the inbox or fail to, independent of SMTP acceptance alone.
How it works
Providers combine authentication, reputation, engagement, and content signals to accept, defer, filter, or reject mail. Operators diagnose deliverability by separating transfer success from foldering outcomes.
Limitations
- Provider filters are opaque and change without public notice.
- SMTP acceptance does not guarantee inbox placement.
Common misconceptions
- Deliverability is only about SPF/DKIM/DMARC.
- A green spam-checker score guarantees inbox placement.
How to verify
- Inspect SMTP responses and bounce classes for acceptance issues.
- Use seed or panel data cautiously to estimate foldering outcomes.
- Correlate authentication, complaint, and engagement signals over time.