Email deliverability is the ability of your emails to reach the inbox rather than spam or a block. In cold outbound it is the difference between a campaign that gets replies and one that quietly disappears.
What decides the inbox
Mailbox providers score sender reputation from authentication, sending behavior, and engagement. Poor authentication, sending too fast from a cold domain, spammy content, and low reply rates all push you toward the spam folder. A brand-new domain blasting volume is the fastest way to burn reputation.
Protecting it
Deliverability is protected by warming the domain, keeping volume measured, cleaning lists to cut bounces, and earning replies, which signal to providers that your mail is wanted. It is why a first cold email should ask for a reply, not carry a link or a hard pitch that trips filters.