Email Deliverability Science: Why AI Warmups Matter in 2025

A practical note from someone watching outbound change in real time.

Over the past year, I’ve had countless conversations with founders, revenue leaders, and SDR managers who all describe the same issue:
“Our emails aren’t landing like they used to.”

Teams keep reworking their copy. They try new tools. They experiment with different send times. Some even change their entire outreach strategy.

But here’s the uncomfortable truth no one wants to admit:

Most email problems have nothing to do with messaging.
They have everything to do with domain trust.

If mailbox providers don’t trust your sending pattern — your emails won’t get through. And in 2025, filters have become far more intelligent and far less forgiving.

Why Deliverability Is Failing for So Many Teams

The reason is simple.
Every provider — Gmail, Outlook, corporate servers — now uses AI-driven systems to evaluate senders.

And these systems care about three core signals:

1. A healthy, gradual volume ramp

Cold domains that suddenly send 200+ emails get blocked immediately.

2. Positive engagement

Opens, replies, forwards — this is what tells inbox filters your emails belong there.

3. Extremely low spam complaints

Even a 0.1% complaint rate can tank your reputation overnight.

When any of these break, no amount of good messaging can save the campaign.

Why the Old Way of “Warmup” No Longer Works

A few years ago, warmup was easy.
People would:

• manually send small batches

• open emails from each other

• reply back and forth

• ask teammates to help

Mailbox providers have outgrown these tricks.

Today, they analyze sender timing, consistency, reply depth, diversity of interactions, domain age, IP pattern — and whether the behavior looks “human.”

Most warmups fail because they look exactly like what they are:
unnatural activity.

The Shift Toward AI-Based Warmup

AI warmup works because it replicates natural behavior at scale and over time.

It does things humans simply cannot:

• gradually adjust sending volume every day

• simulate real conversations

• vary timing to avoid patterns

• interact with a diverse set of inboxes

• detect reputation risk before filters do

• correct patterns automatically

Over the last 12 months, we’ve seen something consistent across teams using structured AI warmup:

• Inbox placement improves by 30–60%

• Spam score drops across Gmail, Outlook, and Proofpoint

• SDR teams become dramatically more productive

• Domains survive longer without degradation

The technology isn’t doing anything magical it’s just doing the basics better than humans can.

Why Ramp Schedules Are the Real Science

One of the biggest mistakes I see is teams trying to scale too quickly.
A safe ramp for a new domain looks something like:

20 → 40 → 80 → 150 → 250 emails/day

But this can’t be static.
It has to change based on:

• bounce rates

• spam signals

• engagement

• blacklist activity

• sequence content

This constant monitoring and adjustment is why AI has become the default approach.

Manual warmup simply can’t keep pace.

The Business Impact: Deliverability = Revenue

Here’s the simplest way to understand it:

If you fix deliverability, everything else becomes easier.
If you ignore deliverability, everything else becomes harder.

A domain with poor reputation will sabotage:

• reply rates

• booked meetings

• SDR productivity

• downstream pipeline forecasts

Outbound doesn’t break at messaging.
It breaks at trust.

What We’re Building at OnePgr

We’ve spent the last year building a deliverability system that makes warmup reliable rather than guesswork.

Our platform now handles:

• intelligent AI warmup

• smart ramp schedules

• ongoing domain health scoring

• spam-trigger detection

• continuous optimization

• human-like engagement patterns
  
  The goal is simple:
  Make email deliverability something you never have to worry about.

Outbound teams should be spending time on conversations not fighting filters.

I’ll leave you with one lesson we’ve seen across every high-performing outbound team:

Your domain reputation is the real asset.
Protect it like one.

When deliverability is strong, outbound scales smoothly.
When deliverability is weak, nothing else matters.

— Rajiv Saxena
OnePgr | onepgr.com