You just registered a new sending domain and you're ready to send. Before you launch your first email marketing campaign, there's a process you can't skip: learning how to warm up email domain sending from scratch.
Skip it, and internet service providers will treat your emails with immediate suspicion. Messages land in the spam folder instead of customers' inboxes, open rates tank, click-through rates drop, bounce rates spike, and in the worst case your domain ends up blacklisted before you've sent a thousand emails.
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What is email domain warm-up?
When you send from a new domain, inbox providers like Gmail, Outlook, and Yahoo have no data on you. Email sender reputation is a score determined by these providers that influences whether your emails reach customers' inboxes or get marked as spam. It's built from signals accumulated over time: engagement metrics, bounce rates, sender history, and unsubscribe rates.
Domain warm-up is the process of gradually building a positive email sender reputation. You start with low volumes to your most engaged subscribers, then increase over 4 to 8 weeks as email service providers learn to trust your sending behavior.
A good email sender reputation increases the likelihood that emails reach subscribers' inboxes and support long-term deliverability. A poor reputation leads to emails being filtered to the spam folder or blocked entirely. There is no shortcut to building it.
Before you start: prerequisites
Authenticate your domain
Three records are required before your first send.
DKIM signs your emails cryptographically, proving they came from your domain and not from spoofed mail servers. Without it, inbox providers can't verify your identity. DKIM has been mandatory for bulk Gmail senders since February 2024.
SPF specifies which mail servers are authorized to send on behalf of your domain. Check your ESP's guidance before adding records manually. Incorrect SPF on shared infrastructure can break alignment and impact deliverability.
DMARC tells inbox providers what to do when emails fail authentication. Start with p=none (monitoring only), then tighten to p=quarantine or p=reject as your sender reputation stabilizes. DMARC is now mandatory for Gmail, Yahoo, and Microsoft. Microsoft made it a hard requirement in April 2025.
If you're using Brevo, domain authentication is handled automatically: it detects your DNS provider and adds all required records. For a full explanation of each protocol, see SPF, DKIM, and DMARC explained.
Clean your list
Sending to invalid addresses produces high bounce rates that directly damage your domain reputation before it has a chance to build. Before warm-up, remove contacts who haven't engaged in 6+ months, scrub invalid addresses, and confirm opt-in status for all subscribers. Explicit opt-in is the single most reliable signal that a subscriber wants your emails. It keeps bounce rates low from day one.
Never send to purchased lists. The hard bounces alone will immediately damage your email sender reputation across the same domain.
The domain warm-up schedule
The schedule below assumes a brand-new domain with no sending history. Adjust based on your target volume.
Week 1, establish sending patterns
Send only to your highest-confidence contacts, people who have recently opted in and are most likely to open, click, and reply. Positive past user engagement during week 1 is the foundation of a good email sender reputation.
Week 2, build momentum
Monitor bounce rates closely. If the bounce rate climbs above 3%, stop and investigate before continuing.
Week 3-4, gradual scale
Continue prioritizing engaged segments. Avoid re-engagement campaigns and cold sends until week 6 or later. They tend to generate low open rates and complaints that will affect email deliverability on a young domain.
Week 5-8, ramp to full volume
Increase toward your target volume at 20 to 50% per step. You can begin introducing less-engaged segments, but watch for any uptick in bounce rates or complaints and pull back if needed.
Never pause for more than 30 days during warm-up. Gaps cause internet service providers to lose confidence in your sending cadence, and you'll need to restart at lower volume. Consistency over time is what builds a high reputation with inbox providers.
What to monitor during warm-up
Google Postmaster Tools
Free and essential. Since Google migrated to Postmaster Tools v2 (September 2025), the primary metric to watch is your spam rate. Keep it below 0.1% daily, and never reach 0.3%, at which point Gmail begins actively filtering or rejecting your mail. The old four-tier reputation dashboard has been replaced by a Compliance Status view (Pass / Needs Work). Register your domain before your first send so data accumulates from day one.
For Outlook visibility, use Microsoft SNDS to monitor IP reputation and complaint data for Hotmail and Outlook recipients.
Sender score and third-party tools
Since Postmaster Tools v2 removed its IP reputation dashboard, external tools matter more than before. Sender Score provides a 0 to 100 reputation score for your sending IP based on complaint rates, sending patterns, and bounce rates. A high reputation score indicates a trustworthy sender and correlates directly with better email deliverability rates. Check MXToolbox weekly for blocklist status. Catching a listing early protects your long-term deliverability and prevents reputation decay.
Bounce rates and complaints
Track hard bounces (invalid addresses, permanent failures) and soft bounces separately. A hard bounce rate above 2% is a warning sign. Above 5%, stop and clean your list. High bounce rates are one of the fastest ways to damage sender reputation early.
Monitor complaints via your ESP dashboard. Even 2 to 3 per 1,000 emails puts you at 0.2 to 0.3%. Investigate and fix the segment before sending more. Catching reputation issues early is always easier than recovering from a poor reputation later.
Common mistakes that derail warm-up
Ramping too fast. To effectively warm up a domain, begin with low volume and increase 20 to 50% daily after the first few days. Abrupt volume spikes trigger spam filters and damage reputation regardless of list quality.
Starting with disengaged contacts. Re-engagement marketing campaigns during warm-up generate low open rates and complaints. Both hurt IP and domain reputation before it's established.
Using spam trigger words. Subject lines and body copy with aggressive promotional language, excessive capitalization, or phrases that trigger spam filters increase the rate at which emails are marked as spam. This is especially damaging before your domain has enough good reputation to absorb the signal.
Inconsistent sending. Mailbox providers build trust from consistent sending behavior. Aim for daily or every-other-day sends rather than large weekly batches.
Cold outreach on the same domain. Cold email produces spam complaints at a much higher rate than opt-in email. Use a separate subdomain and warm it independently. Keep your primary domain reputation protected.
Domain warm-up vs. IP warm-up
Domain warm-up applies to every sender and builds your email sender reputation with inbox providers. IP warm-up applies specifically to dedicated IP addresses, which also start with no sending history.
Most senders don't need a dedicated IP. Brevo's shared IPs deliver 99%+ inbox rates for most subscribers. A dedicated IP only makes sense at 50,000 to 100,000+ emails per week consistently. Below that, the IP address may actually hurt email deliverability rates because there isn't enough volume to build strong IP reputation quickly. See how to set up a dedicated IP in Brevo if relevant.
For a broader set of email deliverability best practices and Brevo's deliverability services, see the linked resources. For Gmail, Yahoo, and Microsoft compliance, see Brevo's sending compliance guide.
Domain warm-up checklist
Before you start:
- SPF, DKIM, DMARC verified. Authentication is the foundation of sender reputation
- List cleaned. Invalid addresses removed, no purchased contacts
- Double opt-in enabled for new subscribers
- Google Postmaster Tools set up, domain registered
- Microsoft SNDS access configured
- Sender Score baseline recorded
During warm-up:
- Bounce rates monitored daily. Pause if above 3%
- Spam complaints below 0.1%
- No gaps longer than 7 days between sends
- No cold outreach until week 6+
- Blocklist check weekly via MXToolbox
After warm-up:
- Monitor Postmaster Tools spam rate weekly. Reputation requires ongoing maintenance
- Maintain consistent cadence to preserve the sender reputation you've built
- List hygiene review every 3 to 6 months
