Cold email playbook
Practical guides on the authentication records that make or break cold email deliverability.
Secondary domains, multi-tool stacks, the 10-lookup ceiling, and why broken SPF silently kills reply rates.
DKIM is the only auth record that travels inside the email itself. Here's why it matters for cold email, what breaks it, and why most operators set it up once and forget it at their own risk.
Misconfigured policies, p=reject disasters, alignment failures, and how DMARC silently kills deliverability.