IP Warming in 2025: The Playbook for Deliverability Pros

Editor’s Note:
This post was created with help from generative AI and reviewed for accuracy and relevance to the LearnLoop Labs community.

Let’s be real.
In 2025, inbox placement isn’t about luck—it’s about discipline. With Gmail, Yahoo, and Outlook tightening the screws on senders, IP warming has gone from “nice to have” to “non-negotiable.” If you’re launching from a new IP and haven’t mapped a warming plan, you’re not just flying blind—you’re headed straight for the junk folder.

This post breaks down what actually works in 2025. Whether you’re warming a single dedicated IP or scaling a new subdomain strategy, the same principles apply: smart ramp-up, airtight technical setup, and relentless focus on engagement. Let’s dig in.

Why IP Warming Is No Longer Optional

A cold IP has no reputation. And in 2025, no reputation equals no trust. ISPs are looking for consistency, authentication, and engagement. Skip the ramp-up, and you’ll likely face spam foldering, throttling, or worse—outright blocking.¹

Warming is how you earn your spot in the inbox. That means:

Start slow (yes, really).
Send only to your hottest segments first.
Monitor KPIs like a hawk (bounce <3%, complaints <0.3%).⁵

And most critically? Prove you’re playing by the rules—SPF, DKIM, DMARC, the whole deal.² ISPs are now enforcing these standards as baseline compliance, not bonus points.³

The Basics: What IP Warming Actually Means

IP warming = gradually increasing your daily send volume from a new or dormant IP.⁶ You’re showing ISPs that you send wanted email, to real people, with real engagement. It’s about predictability, not just volume.

What builds sender reputation:

Authentication (SPF, DKIM, DMARC)²
Consistent sending patterns¹⁶
Engagement (opens, clicks, replies)¹⁸
Low bounces and complaints²⁷

Spam traps, junk content, or a sudden volume spike? Say goodbye to deliverability.²⁰

Avoid These Mistakes (Seriously)

Miss the warm-up or move too fast, and you’ll burn your IP before you even get going. Spam foldering is just the start. Throttling, blacklisting, and delivery freezes can follow.²

And once your rep is damaged, recovery is a slog. ISPs don’t forgive easily. It can take months to climb back from a bad start.³¹ Start smart or start over later.

What You Need Before You Send a Single Email

1. Authenticate Everything
SPF, DKIM, DMARC—fully aligned and properly published.⁵ If your domain isn’t authenticated, ISPs won’t even consider trusting your mail.

2. Nail List Hygiene
Your warm-up list must be:

Fully opted-in (double opt-in preferred)²³
Free from bounces, spam traps, and inactivity²
Cleaned and verified before the first send²

3. Segment for Engagement
Only send to users who have clicked or opened within the last 30 days.⁸ Warm up by targeting those who are most likely to engage.

4. Use Proven Content
High CTR content, clear CTAs, and strong value props. No spammy copy, and absolutely no missing unsubscribe links.³

Warming Schedules That Actually Work

Scenario A: High-Volume Scaling (Target: Millions/month)

Start with 500–2,000/day to your top 30-day engagers.⁷ Then double volume daily until week 2. After that, increase by 25–50% as you expand to 60- and 90-day engaged segments.

Sample Schedule:
Week 1: 500 → 40,000/day
Week 2: 75,000 → 400,000/day
Week 3+: up to 1.75M/day
Full sample in SendGrid, Kickbox, SMTP2GO

Scenario B: Low-Volume Trickled Warming (<100K/month)

Start even slower—think 50–200/day. Double every few days, but keep increases gentle. Target may be just 5,000/day by week 3.⁷

Trickled warm-up may take 2–4 weeks. Use shared IPs if you can’t commit to long-term volume.⁴⁹

You Warmed the IP—Now What?

Keep sending. ISPs expect consistency. Drop off for a few weeks? Your IP cools, and you may need to warm it again.²⁷

Minimum to stay warm:

~100K/month across major ISPs³⁸
~1K/day per provider to avoid decay⁴⁸

Anything less, and you’re better off on a high-quality shared IP pool.⁷

Track What Matters: KPI Benchmarks

KPI	Ideal Target	Mandatory Threshold
Bounce Rate (Hard)	<0.5–1%	<2–3%⁸
Spam Complaint Rate	<0.1%	<0.3%⁵
Open Rate	>20–25%	>10%¹²
Deliverability	>98%	>95%⁸

Tools to use:

Google Postmaster Tools
Microsoft SNDS
Your ESP dashboard + third-party tools like Validity or GlockApps

2025 Compliance Requirements (Read These Twice)

If you send >5,000 emails/day to Gmail or Yahoo, you must:

Authenticate with SPF + DKIM
Publish a DMARC policy (p=none minimum)⁵
Support one-click unsubscribe (RFC 8058)³
Maintain spam rates <0.3% (preferably <0.1%)
Use TLS and proper message formatting

Gmail and Outlook are enforcing these as of Feb 2025. Miss them, and your warm-up means nothing.³⁴

Pro Tips from the Trenches

Register for FBLs (Feedback Loops). ISPs like Outlook give you early spam alerts.¹⁶
Segment your sends by ISP. If Yahoo’s throttling, slow that slice only.⁷
Rotate in new content—but test it first. One bad email can tank your warm-up.⁹
Set up alerts for bounce/spam spikes. Fix fast, or pause your schedule.¹³

Wrap-Up: IP Warming Is Just the Start

Nailing your warm-up gets you in the inbox—but staying there takes work. Deliverability is ongoing reputation management. Keep your list clean, your cadence steady, and your content relevant.

Because in email, trust isn’t earned once—it’s earned every send.