Cold Email Domain & IP Warm-Up Guide

Why Warm-Up Is Essential

When you send email from a new domain or IP address, mailbox providers have no data about your sending behavior. Without a track record, your emails are treated with suspicion — high volume from an unknown sender is the #1 signal of spam.

Warm-up is the process of gradually increasing your sending volume while building a positive reputation. It teaches mailbox providers that your emails are wanted, opened, and clicked — not ignored or marked as spam.

Skipping warm-up almost always results in poor inbox placement, temporary blocks, or permanent blacklisting. The weeks you spend warming up save months of reputation recovery later.

Domain Setup Before Warm-Up

Before sending a single email, ensure your domain is properly configured:

• Dedicated sending domain — use a subdomain (e.g., mail.yourdomain.com) or a separate domain for outreach
• SPF record configured for your sending service
• DKIM enabled with 2048-bit keys
• DMARC set to p=none for monitoring during warm-up
• Domain age — ideally, register the domain 2-4 weeks before starting warm-up
• Website on the domain — even a simple landing page gives the domain legitimacy

For cold email specifically, never use your main corporate domain. A single spam complaint on your cold email domain should not affect your primary email communications.

The Warm-Up Schedule

A conservative warm-up schedule for a new domain:

• Week 1: 10-20 emails per day, only to your most engaged contacts or personal connections
• Week 2: 30-50 emails per day
• Week 3: 75-100 emails per day
• Week 4: 150-250 emails per day
• Week 5: 400-600 emails per day
• Week 6: 800-1,200 emails per day
• Week 7+: Continue increasing by 30-50% weekly until you reach target volume

This schedule assumes good engagement metrics at each stage. If bounce rates exceed 5% or complaint rates exceed 0.1%, reduce volume and investigate before continuing.

For dedicated IP warm-up (if your ESP provides dedicated IPs), follow the same schedule but start even more conservatively — 5-10 emails per day in week 1.

Content During Warm-Up

The content you send during warm-up matters as much as the volume:

• Send to engaged recipients first — people who know you and will open/click
• Encourage replies — ask a question that invites a response. Replies are the strongest positive signal.
• Keep it simple — plain text or minimal HTML during early stages
• Avoid spam trigger words — "free," "limited time," "act now" during warm-up
• Personalize — use first names and reference specific context
• Include only one link — multiple links in early warm-up emails can trigger filters

Monitoring Progress

Track these metrics daily during warm-up:

• Inbox placement rate — use GlockApps or similar tools to test across providers
• Open rate — should be 40%+ during warm-up (you are sending to engaged contacts)
• Bounce rate — hard bounces should be under 2%
• Spam complaint rate — must stay under 0.1%
• Blacklist status — check daily using MXToolbox

If any metric degrades significantly, pause sending for 24-48 hours, then resume at the previous volume level. Patience during warm-up prevents much larger problems later.