How to warm up an IP: a step-by-step lesson

The problem

Ana opened a store with a new domain and a new IP (the address of the sending server). She wants to send 50,000 emails today.

Here is what happens:

1. The IP is new and has no history.
2. The volume is high all at once.
3. Gmail and Outlook get suspicious.
4. Delivery is limited or blocked.

Let's see how Ana avoids this.

Step 1: Understand reputation

A provider is who receives the email, like Gmail or Outlook. Providers give each sender a score, called reputation. Three things count: volume, bounces (returned emails) and spam.

Step 2: Know the two reputations

Which one counts, domain or IP? Both. Domain reputation follows your brand. IP reputation stays with the server address. Ana starts from zero on both.

Step 3: Choose your IP

On a shared IP, you split it with other customers, so you risk noisy neighbors. A dedicated IP is only yours, but it needs constant volume and a warmup. Ana chose dedicated.

Step 4: Warm up in steps

Warmup means sending more in steps to avoid spikes that scare providers. Think of a new credit card:

Credit card	IP
New card, low limit	New IP, sends little
Good history, limit goes up	Good history, volume goes up

Example from the Resend guide for a new domain:

Day	Emails
1	150
3	400
5	1,000
7	2,000

Step 5: Start with active contacts

Ana first emails the people who open the most. That keeps complaints low as volume grows. The rest come later.

How long does it take? For a dedicated IP, AWS says 2 to 6 weeks.

Warm up again when you change domain, IP or provider, or when volume grows a lot.

Step 6: Watch your numbers

Resend's guide uses these references:

• Bounces: below 4%
• Spam: below 0.08%

If they rise, follow this order:

1. Brake: slow down.
2. Investigate: find the cause.
3. Resume: continue only after you fix it.

The result

Without warmup	With warmup
Volume spike	Volume in steps
Providers distrust you	No scary spike
May get limited or blocked	Problems show early, and you can fix them

In the end, Ana reaches 50,000 emails in steps, with no spike.

Try it yourself

Calculate the bounce rate of your last send:

bounce% = bounced / sent * 100

Example: 30 bounced out of 1,000 sent is 3%, which is below the 4% reference.

Checklist:

• [ ] Did I raise volume slowly?
• [ ] Did I start with the people who open the most?
• [ ] Do I track bounces and spam?

Test what you learned: https://thallesaguiar.github.io/ip-warmup-quiz/en/

Sources: Resend Warm-up Guide and AWS SES documentation