Why Email Warmup Matters
When you start sending emails from a new domain or IP address, email providers don't know if you're trustworthy. They watch your sending patterns closely. If you suddenly send thousands of emails without establishing trust first, providers assume you might be a spammer and will block your emails or send them to spam.
Warmup solves this by proving you're a legitimate sender. You start small, demonstrate good engagement, and gradually increase volume. This builds trust with email providers and protects your deliverability.
When You Need Email Warmup
You should warm up your sending reputation in these situations:
New domains or IP addresses: Always warm up when sending from a domain or IP that hasn't sent emails before.
After extended breaks: If your domain hasn't sent emails in 30+ days, restart with a warmup process to re-establish your reputation.
Switching to a dedicated IP: If you're moving from a shared IP to a dedicated IP in SendX (recommended for high-volume senders or if experiencing deliverability issues on shared infrastructure), you'll need to warm up the new IP.
Scaling up significantly: If you're planning to increase your sending volume by more than 50%, use warmup to make the transition safely.
How Email Warmup Works
Email warmup relies on four key factors working together:
Your sending IP address: The server that sends your emails needs to build a good reputation. SendX offers both shared IPs (multiple customers send from the same IP) and dedicated IPs (you have your own IP address).
Your sending domain: The domain in your "from" address (like @yourcompany.com) builds its own reputation separate from the IP.
Your contact list quality: Engaged subscribers who open and click your emails signal to providers that you're sending valuable content.
Email providers (ISPs): Gmail, Yahoo, Outlook, and others each track your reputation independently, which is why warmup must account for different provider volumes.
SendX Warmup Options
SendX offers two warmup approaches based on your needs:
Auto Warmup: Automatically creates provider-specific warmup schedules based on your contact list composition. Best for users who want optimized, hands-off warmup that adapts to your audience's email providers.
Simple Warmup: Uses a straightforward contact-based growth strategy with predictable growth rates (50%/40%/30%/20% by phase). Best for users who want easier planning and prefer to understand exactly what volume will send each day.
Both features are available on all SendX plans. You enable warmup when scheduling your campaign, and SendX automatically handles the gradual volume increases.
Standard Warmup Schedule Reference
Here's the typical warmup schedule SendX follows for dedicated IPs. This gives you an idea of how gradually volume increases over time:
Day | Volume |
1 | 1,000 |
2 | 2,000 |
3 | 4,000 |
4 | 8,000 |
5 | 16,000 |
6 | 32,000 |
7 | 48,000 |
8 | 64,000 |
9 | 96,000 |
10 | 128,000 |
11 | 192,000 |
12 | 256,000 |
13 | 360,000 |
14 | 512,000 |
Your actual schedule may vary based on your list size, engagement rates, and which warmup mode you choose.
Best Practices for Successful Warmup
Start with your most engaged contacts: Begin warmup by sending to subscribers who recently opened or clicked your emails. You'll need to manually segment these contacts or import opener/clicker lists from your previous email platform. High engagement during warmup builds positive reputation faster.
Avoid brand new domains: Don't purchase a domain and immediately start sending emails. Use a domain that's been registered for at least 30 days and has a legitimate website associated with it. Brand new domains raise red flags with email providers.
Send valuable content during warmup: Use real campaigns with genuine value, not test content. Engagement metrics during warmup directly impact your reputation.
Maintain consistency: Don't skip days or stop mid-warmup. Inconsistent sending patterns confuse email providers about your behavior.
Monitor key metrics closely: Watch your open rates, click rates, bounce rates, and spam complaint rates. If complaints exceed 0.1%, pause and review your list quality.
Clean your list first: Remove inactive contacts, invalid addresses, and obvious spam traps before beginning warmup. Bad list quality will sabotage even the best warmup strategy.
One domain at a time: If you have multiple sending domains, warm up each one separately. You can warm up 2 to 3 domains simultaneously, but only if using slower warmup speeds to avoid overwhelming your system.
Speed up with prior reputation: If you're migrating to SendX with a domain that's already warmed up on another platform, you can choose a faster warmup schedule or start from an advanced day to save time.
Important Notes and Limitations
Warmup applies to both IPs and domains: Even if your IP is warmed up, a new domain still needs warmup. Similarly, a warmed domain on a new dedicated IP requires warmup for that IP.
Shared vs dedicated IP considerations: On shared IPs, your reputation is partially affected by other senders. If you experience deliverability challenges due to shared reputation or send high volumes (100,000+ emails weekly), consider upgrading to a dedicated IP. Note that a dedicated IP requires warmup when you first switch to it.
Manual enablement required: Warmup doesn't happen automatically. You must enable Auto Warmup Mode or Simple Warmup Mode when scheduling your campaign.
Deliverability may fluctuate initially: During the first few days of warmup, you might notice temporary dips in open rates or inbox placement. This is normal and stabilizes as your reputation builds.
Breaking warmup has consequences: If you stop mid-warmup or skip days, email providers may view your sending pattern as suspicious, potentially harming your reputation more than if you'd never started warmup.
What Happens If You Skip Warmup
Skipping warmup when you should be warming up leads to serious deliverability problems:
Spam folder placement: Your emails bypass inboxes and land directly in spam, where most recipients never see them.
Provider blocks: Gmail, Yahoo, or other providers may temporarily or permanently block emails from your domain or IP.
Damaged reputation: Poor initial reputation is difficult to repair and requires extensive re-warming, often taking longer than if you'd warmed up properly from the start.
Wasted campaigns: Your carefully crafted emails and segmented audiences deliver no results because recipients never receive them.
Common Questions
Q: How long does warmup take?
It depends on your list size and engagement. A typical warmup takes 2 to 4 weeks for most senders. Larger lists or lists with lower engagement may need longer.
Q: Can I send to my entire list during warmup?
Not immediately. Warmup starts with a small segment and gradually increases. By the end of warmup, you'll reach your full list. The warmup schedule determines how many contacts receive emails each day.
Q: What if I have an already-warmed domain from another platform?
You can choose a faster warmup speed or start from an advanced day in Simple Warmup. However, starting with at least a brief warmup (even 7 to 10 days) is safer when switching platforms, as different sending infrastructure may affect reputation.
Q: Do I need to warm up for every campaign?
No. Once your domain and IP are warmed up, you can send at your established volume without re-warming, as long as you maintain consistent sending patterns. Re-warm only if you take breaks of 30+ days or significantly increase volume.
Q: What's the difference between warming up my domain vs my IP?
Your domain (like @yourcompany.com) and your IP address build separate reputations. Email providers track both. If you use a dedicated IP, you must warm up both the domain and the IP. On shared IPs, the IP is already warmed, but your domain still needs warmup.
Q: Can I speed up the warmup process?
While you can choose faster warmup speeds if you have prior sending history, we don't recommend rushing warmup for brand new domains or IPs. The schedule exists to protect your deliverability. Going too fast defeats the purpose and risks damaging your reputation.
Next Steps
Ready to start warming up your domain? Choose the warmup approach that fits your needs:
Set Up Auto Warmup: For provider-optimized, hands-off warmup that adapts to your contact list.
Set Up Simple Warmup: For straightforward, predictable contact-based warmup with clear growth rates.
Need help with deliverability or have questions about your specific warmup situation? Contact our support team at support@sendx.io.