Never cold-email from free providers (gmail.com, outlook.com). They flag commercial outreach aggressively and you can't authenticate properly. Always use a custom domain you own.
Why free providers fail
Their ToS forbids commercial outreach. SPF/DKIM/DMARC can't be fully configured. Volume gets throttled immediately.
Custom domain workflow
Own a sending domain (often a secondary domain, not your main brand domain). Configure SPF, DKIM, DMARC. Warm it for 4–6 weeks.
Why secondary domains
Protect your primary domain from any deliverability risk. Use lookalikes (try-yourbrand.com, getyourbrand.com).
How SendroAI Fits In
SendroAI requires custom-domain inboxes and integrates with warm-up to protect deliverability from day one.