What it means
Email deliverability is whether your emails reach the inbox, rather than spam or nowhere at all. It rests on three things. Authentication proves you are allowed to send from your domain, through SPF, DKIM and DMARC. Reputation is how mailbox providers rate your domain and inboxes, built from bounces, spam complaints and engagement.
Sending habits count too: sudden volume spikes, broken links and spammy formatting all work against you. A campaign with good copy and poor deliverability looks like a copy problem until someone checks the inboxes.
Delivery and deliverability are different numbers. Delivery means the receiving server accepted the email. Deliverability means it reached the inbox, so a campaign can show near-perfect delivery while much of it lands in spam. Inbox placement is measured with seed tests across mailbox providers, because sending tools report delivery rather than placement.
How we use it
The setup we run before any campaign, from provider limits to warm-up presets and the weekly health check, is in our cold email deliverability checklist.