You've set up a new sending domain. You've got a list of 5,000 contacts ready to go. You're tempted to send to all of them on day one.
Don't.
Domain warmup is the process of gradually increasing your sending volume from a new domain to establish trust with inbox providers. Skip it and you'll hit spam folders — or worse, get your domain blacklisted before you've sent a single real campaign.
Here's how to do it right.
Why Warmup Matters
Inbox providers — Gmail, Outlook, Yahoo — track the history of every sending domain. A new domain has no history. No history means no trust. No trust means uncertain placement.
When you send a large volume from a cold domain, inbox providers don't know whether you're a legitimate business or a spammer. Their response is the same: send it to spam and see if anyone complains.
Warmup changes this. By starting small and gradually increasing volume while maintaining strong engagement metrics, you build a reputation that inbox providers can rely on.
How Long Does Warmup Take?
For most B2B senders:
- Week 1–2: 100–500 emails/day
- Week 3–4: 500–2,000 emails/day
- Week 5–6: 2,000–10,000 emails/day
- Week 7+: Full volume
The pace depends on your engagement rates. If your opens and clicks are strong and complaints are zero, you can accelerate. If you're seeing soft bounces or low engagement, slow down.
Step-by-Step Warmup Process
1. Authenticate your domain first
Before you send a single email, make sure your domain has valid authentication records. This tells inbox providers that you're the legitimate owner of the domain and that you've configured it correctly. Without it, warmup is pointless — you'll be building reputation on a broken foundation.
2. Start with your most engaged contacts
Your warmup emails need to perform well. Send to people who know you and are likely to open. These are your existing customers, recent signups, or anyone who's engaged with you recently. Do not start with cold lists.
High open rates and low complaints during warmup build positive reputation quickly. The opposite builds negative reputation just as quickly.
3. Send consistently
Inbox providers respond well to consistent patterns. A domain that sends 200 emails every day looks more legitimate than one that sends 0 for a week then 2,000 on a single day. Keep a regular cadence, even if the volume is low.
4. Monitor closely
During warmup, watch your metrics daily:
- Bounce rate: Should stay below 2%. Spikes mean you're sending to bad addresses.
- Spam complaint rate: Should stay below 0.1%. Anything higher slows your warmup significantly.
- Open rate: Should be above your industry average. Low engagement signals poor list quality.
If any of these go wrong, pause and investigate before continuing.
5. Use a separate subdomain for different sending types
If you send both marketing and transactional emails, use separate subdomains: marketing.yourdomain.com for campaigns, mail.yourdomain.com for transactional. This isolates your reputation pools — a deliverability problem with one doesn't affect the other.
Common Warmup Mistakes
Sending to purchased or scraped lists during warmup
These lists have high bounce rates and spam complaint rates. They'll destroy your reputation before it's established.
Going from zero to full volume too quickly
Even if your early sends perform well, jumping volume too fast triggers spam filters. Follow a gradual ramp.
Ignoring soft bounces
Soft bounces (temporary failures, like a full inbox) during warmup can indicate deliverability problems. Track them and investigate patterns.
Not warming up after a long break
If you haven't sent from a domain in 6+ months, your reputation may have decayed. Treat it like a new domain and re-warm.
After Warmup
Once you've warmed up successfully, maintaining your reputation requires ongoing attention:
- Keep bounce rates below 2%
- Keep complaint rates below 0.1%
- Suppress inactive contacts regularly
- Monitor your domain health for authentication failures or new senders
Taildove handles the monitoring automatically — authentication, DMARC reports, bounce suppression, and reputation alerts are built in. The warmup itself still requires deliberate list management and patience.
Two to four weeks of careful warmup is a small investment for a domain that delivers reliably for years.