Domain Warmup & Verification

When you start sending from a new domain, Gmail, Outlook, and Yahoo don’t trust it. A brand new domain has no sending history — no track record of sending emails that people actually want to receive. To these providers, your domain looks the same as a spammer’s fresh domain.

Warmup is the process of gradually building that trust. You start by sending a small number of emails (5-10 per day), then slowly increase over 2-4 weeks. During this period, the emails you send need to get opened, replied to, and not marked as spam. This positive activity signals to Gmail and Outlook: “this domain sends real emails that real people want.”

By the end of warmup, your domain has earned a reputation. Gmail starts delivering your emails to the inbox instead of spam. You can now scale up to full sending volume.

That reputation is fragile. And the fastest way to destroy it is to send to addresses that bounce.

The damage is especially bad during warmup because your domain has no track record to fall back on. An established domain with months of clean sending can survive a small bounce spike. A warming domain with 3 weeks of history? One bad send is enough to lose everything.

And the bounces that hurt most are delayed bounces — catch-all servers that say “delivered” on day 1 but reject the email on day 3. By the time you see the damage, it’s already done. Full delayed bounce guide →

This applies every time you add new leads — not just during initial warmup. Even after warmup is complete, loading unverified leads risks the reputation you built. Every new batch gets verified first. No exceptions.

If you’re running multiple domains in rotation, verify once and split the safe file across domains. One verification covers all your sending domains.