If you’re launching a new ESP like Braze, moving to a dedicated IP, or making major changes to how you send email, you need to warm up your IP. Skip this step and you risk low inbox placement, high bounce rates, or full-on blacklist territory.

What Is an IP Warmup?

An IP warmup is the process of gradually increasing email send volume from a new or inactive dedicated IP address. Internet Service Providers (ISPs) don’t trust new IPs by default, they need to observe your behavior, engagement rates, and consistency before allowing you full access to their users’ inboxes.

Think of it like building a credit score from scratch. You start small, prove you’re responsible, and earn your way to higher limits.

When You Need an IP Warmup

If you’re using a dedicated IP, you absolutely need to warm it up. There’s no way around it. ISPs don’t trust new IPs by default, and a cold send from an unproven address is a fast track to the spam folder.

What about shared IPs?

Being on a shared IP means your email reputation is tied to every other sender using that address. Your deliverability is only as strong as the weakest sender on the IP. If someone on that shared address sends spam or triggers high complaint rates, your emails can suffer the consequences—even if your program is perfectly clean.

Many shared IPs end up on blacklists because of one bad sender. And when that happens, your emails will start landing in spam, not because of what you did, but because you're sharing space with someone who tanked the IP's reputation.

In short: shared IPs are convenient, but risky. If you care about long-term deliverability, control, and inbox placement, migrating to a dedicated IP and warming it up properly is the move.

Here’s when to initiate an IP warmup:

• New Braze account or ESP migration
  You’re moving to a new platform with a fresh IP, ISPs don’t recognize it yet.
• Moving to a dedicated IP
  You’ve outgrown shared IPs and want full control, but that new IP is unknown to inbox providers.
• Major sending changes
  If you’re ramping up volume significantly, changing your sending domain, or shifting verticals (e.g., from eCommerce to healthtech), ISPs may flag you for unusual behavior.

How IP Warmup Works

Warming up an IP means more than just sending slowly, it’s about building reputation with intentional volume, audience, and timing.

1. Start with Low Daily Volume

Begin with 50–500 emails/day depending on your total audience size. For example, a brand with 500,000 subscribers might start with 500/day and double volume every 3–4 days.

Braze recommends a structured 18-day warmup schedule, starting with just 50 emails on day one and roughly doubling daily until you hit your desired volume. For example, day five should reach 5,000 emails, day ten hits 100,000, and by day fifteen, you’re at 1 million per day. Consistency is critical, skipping days or sending irregular volumes can tank your deliverability.

See Braze’s full warmup guidance here

2. Use Only Highly Engaged Segments

Send first to your most engaged users, those who opened or clicked in the last 14–30 days. This signals high engagement to ISPs and builds trust fast.

Avoid sending to:

• Cold subscribers
• Unverified contacts
• Purchased or scraped lists (obviously)

3. Maintain a Consistent Cadence

Don’t send for three days, then go silent. ISPs want to see predictable, stable patterns that’s how they know you’re not a spammer. Weekends count too. If you’re warming up, try to send 5–7 days per week.

Even after warmup, try to maintain a stable daily cadence. If you go silent for a month, ISPs may reset your reputation, forcing you to start the warmup all over again.

Transactional vs. Marketing Domain IP Warmups

This is where things get nuanced and where most brands mess up.

Marketing Email IP Warmups

Marketing sends are predictable by nature. You’re usually sending campaigns 2–5x/week, and you’re in full control of timing and volume.

What this looks like during warmup:

• Start with 250 marketing emails/day to your engaged segment
• Ramp by 1.5× every 3–5 days
• Monitor opens, clicks, bounces, and complaints daily
• Avoid big jumps (e.g., 500 → 5,000 in one day)

Transactional Email IP Warmups

Transactional sends, like password resets, receipts, order confirmations aren’t scheduled. They’re triggered by user actions, and that creates two challenges:

1. Volume spikes are unpredictable
   Imagine your ecommerce flash sale goes viral. You suddenly go from 500 receipts/day to 5,000. That spike can flag your IP if you’re in the middle of a warmup.
2. Low consistency = poor ramping
   A Monday burst, followed by three quiet days, doesn’t build trust. Even if your content is clean, the irregular pattern looks risky.

How to handle it:

• Set up a separate IP or subdomain just for transactional emails
• Try to pre-warm the IP with simulated load if possible (e.g., sending dummy confirmations to test accounts)
• Gradually roll out your transactional volume across cohorts (e.g., 10% of new orders → 25% → 50%…)

Example: A fintech app launches a new feature and expects a spike in verification emails. Instead of routing all traffic through the new transactional IP, they stagger the rollout to 10% of users, while continuing to warm up the IP steadily. This prevents throttling or blocks from Gmail and Microsoft.

Pro Tips for a Successful IP Warmup

• Authenticate your domain with SPF, DKIM, and DMARC before sending a single email
• Segment by ISP for review when possible warm up Gmail, Yahoo, Outlook separately based on known breakdowns
• Avoid full list sends until you’re 100% ramped and metrics are clean
• Watch your metrics like a hawk: spam complaints, bounce rates, and blocklists can tank your reputation
• Send daily or near-daily during warmup as email trust is built through steady, consistent behavior

IP Warmup Is Not Optional

If you’re scaling your email program, changing tools, or sending from a new IP, warming up is critical. You’re not just earning access to inboxes, you're building a reputation that determines your deliverability for months to come.

Need Help With Your Warmup Strategy?

Whether you’re using Braze, Klaviyo, SFMC, or another ESP, IP warmups are just one step of many in migrating and setting up a new CRM.

Contact us to get started.