You’ve got your domain, your DNS records are properly configured, and your emails are ready to send. But if you start blasting hundreds of messages from day one, your chances of landing in spam skyrocket. Warming up your domain is not optional, it’s a must for protecting your sender reputation and getting into inboxes.
Warming up a domain is one of the most overlooked parts of email outreach, especially for sales and marketing teams eager to launch email campaigns fast. But starting too strong can backfire. If you begin sending high volumes from a cold or newly registered domain, your emails are likely to be flagged or filtered. That hurts your sender reputation and delays your progress.
This post is based on our recent webinar “Message Received: How to Optimize Your Email Deliverability.” We discussed real-life examples and actionable advice to improve email success. If you want to learn more, make sure to listen to the full webinar here.
Key Takeaways
- Deliverability starts long before you send your first email.
- Proper domain setup and authentication (SPF, DKIM, DMARC) are essential.
- Warming up your domain gradually helps avoid spam filters.
- A clean, validated, and segmented list protects your sender reputation.
- Personalization, content variety, and engagement signals improve inbox placement.
- New rules from providers like Google and Microsoft require unsubscribe options.
Why Domain Warm-Up Matters
Email providers are constantly monitoring sending behavior. If a domain that’s new or has been inactive suddenly starts sending in large volumes, it raises a red flag. Spammers often use this tactic, so even if you’re a legitimate sender, you can be treated as suspicious.
Warm-up tells providers that your activity is intentional and responsible. It helps build a strong sender reputation gradually, so your emails are seen as trustworthy.
What Happens If You Don’t Warm Up
Failing to warm up your domain can have immediate and long-term consequences. Without a gradual introduction to mailbox providers, your sending activity may look suspicious, even if you’re doing everything else right.
- Your emails may land in spam folders or be blocked entirely
Mailbox providers use algorithms that detect abnormal sending patterns. If you go from zero to hundreds of emails per day, your messages may be flagged as potential spam or blocked before they reach the inbox. - Your bounce rates could spike, harming your sender score
A high volume of undeliverable messages tells providers your list may not be trustworthy. Even a few days of high bounce rates can damage your reputation and delay your ability to scale. - You might trigger throttling limits or receive temporary suspensions from your email service provider
Many ESPs have internal limits to protect their networks. If you exceed those limits suddenly, your account could be throttled or temporarily restricted, disrupting your campaign schedule. - Worse, your domain reputation could take a hit that’s hard to recover from
Domain reputation builds slowly and is difficult to repair once it’s been harmed. If providers associate your domain with spam-like behavior early on, your future campaigns, no matter how well executed, could struggle to get delivered at all.
Step-by-Step Warm-Up Strategy
Start small
Begin with a small batch of 20 to 50 emails per day. These messages should be sent to contacts who are most likely to open and engage; people who already know your brand, have opted in, or have interacted with you recently. These early opens and replies send a positive signal to mailbox providers and help build your domain’s credibility.
Increase gradually
Add 20 to 30 percent more emails every 2 to 3 days. For example, if you start with 50 emails on Day 1, you might send 65 on Day 4, 85 on Day 7, and so on. Continue this gradual scale-up until you reach your intended daily send volume. Monitor carefully and if your bounce rate climbs or engagement drops, pause and adjust before increasing further.
Diversify content
Avoid sending identical templates. Even slight changes in subject lines, greetings, or calls to action help. Use personalization fields like name, company, or role. Tools like Spintax can help you insert variations so each message looks and feels unique while delivering the same core message.
Spread out your sends
Space out your emails during working hours instead of delivering them all at once. Use scheduling features in your sending platform to distribute messages across the day. Sudden bursts of identical sends look robotic and can trigger spam filters. A slow, steady rhythm mimics human behavior.
Monitor key metrics
Track bounce rates, open rates, click-through rates, reply rates, and spam complaints daily. A spike in bounces or spam reports means something’s wrong. Stop increasing your volume and address the issue. High engagement means you’re on the right path and can continue scaling.
Don’t skip the basics
Your technical setup must be correct before sending your first email. SPF, DKIM, and DMARC are essential for proving your identity. Without them, mailbox providers may block or filter your emails no matter how clean your warm-up process is.
Consider a subdomain
If your main domain is already being used for other business functions or has a history that might affect deliverability, create and warm a subdomain (like outreach.yourcompany.com). This gives you more control over your sending reputation and allows you to isolate risk while keeping your primary domain protected.
Final Thoughts
Warming up your domain isn’t just a box to check. It’s a critical part of building email credibility and ensuring your outreach efforts aren’t wasted. By starting small, staying consistent, and focusing on positive engagement, you’ll set yourself up for long-term email success.
Want more deliverability best practices? [Listen to the full webinar here] for real-world examples and expert insights.
