No warm-up schedule has ever been published

by Francis Rozange | Sep 8, 2026 | Email Marketing

Abstract 3D render: an unmarked luminous ramp rising beside a ladder dissolving into dust

Look for a warm-up schedule. You will find dozens, all different, all presented with the same confidence.

Day 1, fifty messages. Day 2, one hundred. Day 3, two hundred and fifty. Double every two days. Segment by operator. Write only to your most engaged contacts for two weeks.

None of those tables has a source. No mailbox provider has ever published a warm-up schedule, a starting volume, or a progression curve.

Proof by absence

It can be verified in thirty seconds, and it is conclusive.

The word “warm” does not appear once in Google’s sender guidelines, nor in their FAQ. Google does not even name the concept.

Yahoo mentions it once, in passing, as a possible cause of an error: “You may have setup the IP you are using to send email very recently and did not increase the email traffic slowly.” No figure.

Microsoft does not discuss it in its sender documentation. The IETF has never covered the subject in any RFC.

As of September 2026, then, there is no primary source publishing a warm-up table. What the market calls “the warm-up protocol” is an editorial construction copied from one article to the next for fifteen years.

What Google actually writes

The section exists, and it is titled “Increase sending volume slowly to avoid delivery problems”. It gives no volumes, but it gives principles, and those principles are more useful than a table.

“These factors affect how quickly you can increase sending volume: Amount of email sent: The more email that you send, the more slowly you should increase sending volume. Frequency of sending email: You can increase the sending volume more quickly when you send daily instead of weekly.”

Read the second line twice. Sending every day lets you climb faster than sending every week. Regularity matters more than volume, which condemns the big monthly send in advance.

Then the recommendations, two of which are operational:

“Send email at a consistent rate. Avoid sending email in bursts.”

“Avoid introducing sudden volume spikes if you do not have a history of sending large volumes. For example, immediately doubling previously sent volumes suddenly could result in rate limiting or reputation drops.”

That is the only pacing guidance Google publishes: do not double at once. Not “double every two days”, which is exactly what the circulating tables recommend.

And the feedback loop, which replaces any schedule to advantage:

“If messages start bouncing or start being deferred, reduce the sending volume until the SMTP error rate decreases. Then, increase slowly again.”

The pace is not in a table. It is in your rejection logs, updated hourly, free of charge.

The only figure published by a primary source

It comes from M3AAWG, the body bringing together mailbox providers and anti-abuse actors, in version 4.0 of its sender best common practices, updated in August 2026.

“Start low and slow; increase sending volume slowly. (Consider 6 weeks of warm-up as an average.)”

Six weeks on average. That is a duration, not a volume, and it is presented as an order of magnitude. M3AAWG publishes no day-by-day table, and its IP guidance stays just as general: “Senders should have a well-defined process for warming IPs to be introduced to a dedicated environment and should follow it consistently.”

A defined process, consistently followed. Not a universal one.

The sentence that condemns an entire industry

The same document, in its “Domain Warming” section, contains a line the warm-up tool vendors never quote:

“Artificial warming practices are not recommended and may be illegal.”

Artificial warming is what the networks of mailboxes sell: accounts that write to each other, open each other, reply to each other and pull each other out of the junk folder, in order to simulate the engagement of a real list.

The mailbox providers’ own body calls that practice not recommended and possibly illegal. It belongs to the same family as what M3AAWG condemns in cold email: making a filter mistake one thing for another.

M3AAWG also makes a point that is often forgotten: “When sending from a new subdomain, to be safe, domain warming is recommended even if the organizational level domain already has an established reputation.” A new subdomain starts from zero, however old the parent domain.

The figures in circulation, and where they really come from

One number comes up everywhere: forty-five days. It exists, it is published, and it does not mean what people make it mean.

It comes from Amazon SES documentation, describing how its own product works: “Automatic IP warmup is a time-based process. The warmup percentage steadily increases over 45 days, independently from your sending volume.”

That is a traffic-shifting parameter at one given provider, not an ecosystem rule. The same page publishes a far more honest range about reality: “For some email providers, you can establish a positive reputation in around two weeks, while for others it may take up to six weeks.”

Two to six weeks depending on the operator, without knowing which is which. That is exactly the degree of uncertainty you are dealing with.

What to do tomorrow morning

If you are starting a new sending domain, forget the table and set three rules.

A steady cadence rather than a target volume. Sending a thousand messages a day beats sending seven thousand once a week, and Google writes as much.

A progression that never doubles from one day to the next, with a step back the moment temporary rejections appear. The signal is immediate and it is free. It is on that signal that Sestaro freezes the volume ramp, with bounce and refusal thresholds announced in advance rather than discovered on a Monday morning.

And a starting population that actually asked you for something. That is the one point where every primary source agrees: warm-up does not manufacture reputation, it reveals the one your list already earns you.

Finally, if a provider sells you a guaranteed warm-up in ten days, ask for the source. If they mention a network of mailboxes exchanging messages, you now know what the mailbox providers’ own body thinks of it, and you know the sentence contains the word “illegal”.

Sources

LaFactory works email on the evidence: headers, DNS records, rejection logs. No open rate promises, ever. Get in touch for a deliverability audit.