Cold Email Deliverability Fundamentals: Secondary Domains, SPF/DKIM/DMARC, Warm-Up, and List Hygiene
Your cold email is worthless if it never reaches the inbox. This guide covers the infrastructure that decides whether it does: why you should never send outreach from your main domain, how to choose and age secondary domains, setting up SPF, DKIM, and DMARC correctly, warming up new mailboxes, holding sensible volume limits, and keeping lists clean — with the non-obvious traps that quietly wreck sender reputation.