Mailbox warmup guide for cold outreach

A practical ramp schedule for new Google, Microsoft, and SMTP mailboxes before sequences go live.

What warmup actually does

Warmup builds sender reputation by showing providers a pattern of legitimate, low-risk sending with real engagement. Skipping warmup on a fresh mailbox often produces high bounce or spam rates in the first week.

Week 1: establish identity

Send 10-20 emails per day to known contacts or internal addresses. Focus on plain-text, conversational messages. Confirm SPF, DKIM, and DMARC pass on every provider you target.

Week 2-3: controlled ramp

Increase by 10-20 emails per day per mailbox while monitoring bounces and spam placement. Pause the ramp if hard bounces exceed 2% or replies turn sharply negative.

When to attach sequences

Most teams can attach light sequence volume after 2-3 weeks of clean signals. High-risk domains or purchased lists need longer warmup and stricter list hygiene first.

Warmup mistakes to avoid

• Jumping from 0 to 200+ sends on day one.
• Using the same template for every warmup message.
• Ignoring bounces from invalid addresses in the ramp period.
• Running warmup and full campaigns on one mailbox simultaneously without caps.