Email deliverability is the measure of whether your messages actually land in the recipient's inbox versus being filtered into spam, deferred, or rejected outright. You can write the perfect cold email, but if it never reaches the inbox, none of it matters.
Deliverability is shaped by your sender reputation, your bounce rate, authentication setup (SPF, DKIM, DMARC), sending volume and consistency, and the content of your messages. Sending to invalid addresses, blasting high volume from a cold domain, or using spammy phrasing all degrade it. Good list hygiene through email verification and steady, personalized sending protect it.
For job seekers, the practical takeaway is simple: verify addresses before sending, don't blast, and keep messages genuine. Protecting deliverability is what ensures a hiring manager actually sees your email at all.