Also known as: Inbox Placement
The ability of your email to actually reach recipients' inboxes rather than being blocked or filtered to spam.
Deliverability is the broad measure of whether your mail reaches the inbox. It is more demanding than mere "delivery": a message can be accepted by the server (delivered) yet land in the spam folder (not delivered to the inbox). True deliverability means inbox placement.
It rests on three pillars: authentication (SPF, DKIM, DMARC proving you are who you say), reputation (your history of clean, engaged sending), and list quality (mailing real, consenting, interested people). Weakness in any one drags down the others.
List quality is the pillar you control most directly. Verifying addresses and practising list hygiene keeps bounces and complaints low, which protects reputation, which protects inbox placement.
A trust score that mailbox providers assign to your sending IP and domain, which determines whether your mail reaches the inbox.
An email-authentication standard that lets a domain list which servers are allowed to send mail on its behalf.
An email-authentication standard that adds a cryptographic signature proving a message was not altered in transit.
A policy standard that builds on SPF and DKIM to tell receivers what to do with mail that fails authentication.
See it in action
Check any address against BounceShift's multi-layer engine — syntax, MX, disposable, and role checks free, with full SMTP verification on signup.