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A brand-new sending domain has no reputation. To Gmail, Yahoo, and Microsoft, you're an unknown, and unknown senders are treated with suspicion. Send 10,000 emails on day one and you'll be permanently flagged before lunch.
Warm-up is the controlled process of building reputation by sending small, gradually increasing volumes to engaged recipients. Done right, it takes 30 days. Done wrong, you spend the next 6 months recovering, or buy a new domain.
This guide gives you the exact schedule, what to send, and the mistakes that wreck most warm-ups.
Why Warm-Up Matters
Mailbox providers measure two things for new senders:
- Volume consistency: sudden spikes look like compromised accounts or spam runs.
- Engagement quality: opens, clicks, replies, and forwards prove humans want your mail.
Skip warm-up and you trigger volume-based throttling within the first hour. Even if your authentication is perfect (check that first with the domain health check).
Domain Warm-Up vs IP Warm-Up
| Domain warm-up | IP warm-up | |
|---|---|---|
| What it builds | Reputation tied to your from domain |
Reputation tied to the sending IP |
| Who needs it | Anyone with a new domain or subdomain | Senders on dedicated IPs (typically 100K+/month) |
| Time | 3–4 weeks | 4–8 weeks |
Most senders only need domain warm-up, because your ESP's shared IPs are already warm. If you're on a dedicated IP, you need both, and they should happen in parallel.
The 30-Day Domain Warm-Up Schedule
Targets assume you're sending to a clean, engaged list. Adjust down if your engagement is weak. For cold email, the domain and inbox planner works out the inboxes and warm-up weeks for a daily volume.
| Day | Daily volume | Audience | Goal |
|---|---|---|---|
| 1–3 | 20–50 | Your most engaged contacts (opened in last 30 days) | Establish identity, get opens and replies |
| 4–7 | 100–200 | Engaged + recent signups | Build a consistent baseline |
| 8–14 | 500–1,000 | Engaged segment, daily growth | Expand without spikes |
| 15–21 | 2,000–5,000 | Add 90-day engaged contacts | Increase volume, maintain >20% open rate |
| 22–30 | 10,000–25,000 | Engaged + recent inactives | Approach normal volume |
| 31+ | Full volume | Full segmentable list | Maintained reputation |
Two rules that override the table:
- Never increase volume more than 2× day-over-day. A jump from 500 to 5,000 reads as a compromised account.
- Watch engagement, not just volume. If open rate drops below 15% on any day, hold volume flat until it recovers.
Picking Your First Recipients
The first 1,000 messages set the tone. Send them to:
- Internal team and known contacts who will open and reply.
- Customers from the last 30 days, who recognize you.
- Recent signups with a confirmation or onboarding email.
Avoid in week one:
- Cold contacts.
- Anyone who hasn't engaged in 6+ months.
- Purchased or scraped lists (always avoid these).
- Re-engagement campaigns to dormant subscribers.
Engagement Signals to Optimize
Mailbox providers care most about:
- Replies: strongest positive signal. Plain-text 1:1 onboarding emails get the best reply rates.
- "Move to inbox": ask early recipients to do this if you land in promotions/spam.
- Adding you to contacts: include a P.S. asking for this.
- Clicks on real content links, not tracking pixels.
A 30%+ open rate and 1%+ reply rate during week one will warm a domain faster than any volume schedule.
Common Warm-Up Mistakes
- Starting with a marketing newsletter. Use transactional or 1:1 mail first, which gets better engagement.
- Sending from a brand-new TLD on day one. Wait at least 48 hours after DNS propagation before any send.
- Skipping DMARC. Set up SPF/DKIM/DMARC before day one. See How to Fix SPF, DKIM, and DMARC.
- Pausing for the weekend. Inconsistent volume looks suspicious. Send every day, including weekends, at lower volume.
- Ignoring bounces. Hard-bouncing 5% on day three tells providers your list is junk. Verify before sending.
Tools & Monitoring During Warm-Up
What to watch daily:
- Google Postmaster Tools: domain reputation, spam rate, authentication results.
- Bounce rate: keep under 2%.
- Complaint rate: keep under 0.1%.
- Inbox placement: seed-list test every 3 days.
MailVitals tracks authentication, blacklists, and reputation continuously so you spot a warm-up going sideways before it derails.
FAQ
How long does email warm-up take? A domain warm-up takes 3–4 weeks for typical B2B and B2C senders. Dedicated IPs add another 2–4 weeks. Cold outreach domains often need 4–6 weeks before sending to truly cold contacts.
Can I skip the warm-up if my old domain is warm? No. Reputation is per-domain, not per-account. A new subdomain on a warm root domain inherits some trust but still needs its own ramp.
What if I see spam complaints during warm-up? Stop volume increases immediately. Cut to your most engaged segment until complaints drop below 0.1% for three consecutive days. Then resume the schedule from the previous step.
Do I need a dedicated IP for warm-up? Only if you send 100,000+ emails per month consistently. Below that, a shared IP from a reputable ESP almost always outperforms a dedicated IP, even after warm-up.
Bottom Line
Warm-up is patient, boring, and the most important 30 days a new sending domain will ever have. Follow the schedule, prioritize engagement over volume, and don't skip any steps because you're in a hurry.
Sources
- Email sender guidelines (Gmail Help), Google on raising volume slowly, sending daily rather than weekly, and avoiding sudden doubling.
- Outlook.com Postmaster: Troubleshooting, Outlook.com on new IPs having no reputation and ramping over a couple of weeks while complaints stay low.
- Sender Requirements and Recommendations (Yahoo Sender Hub), Yahoo's note that a recently set-up IP which did not raise traffic slowly can trigger its volume errors.
- M3AAWG Senders Best Communications Practices, Version 3.0, industry practice for consent and volume when starting a new sending stream.