Written by
Tim Collins
Published on
28 August 2026
Across this series we have built up to a single awkward fact. Domain reputation is calculated from recent behaviour, several different parties are calculating it, and when it slips it takes your invoices and quotes down with your campaigns.
Follow that through and you arrive at an uncomfortable conclusion for anyone who sends in bursts. If reputation only reflects the last few weeks, then a domain that goes quiet between campaigns has nothing to show the providers when they look. Every campaign starts from close to nothing, and the first few thousand emails of every send are spent rebuilding standing you already had.
Domain warming is the answer to that, and the reason we leave it running rather than switching it off once it has done its initial job.
What warming does
We warm every new sending domain for 30 days before a client's first campaign, and we wrote about that initial ramp separately in why we warm every sending domain for 30 days. The mechanism is the same whether it is running as an initial ramp or as ongoing maintenance.
A small, steady volume of genuine mail goes out from your domain each day. It goes to a large private network of real mailboxes rather than to your customers, so none of it touches your list. Those messages get opened, replied to, and marked as wanted. If one lands in junk, it gets pulled back into the inbox.
Every one of those actions is a positive signal recorded against your domain, and they are precisely the signals the providers weigh most heavily. What they see is a sender who mails consistently and whose mail people engage with. That is the pattern they reward, and warming produces it deliberately rather than hoping your sending schedule happens to produce it by accident.
Why it is not a task you tick off
This is where most people get it wrong, and it is an easy mistake because almost every other piece of email infrastructure genuinely is a set-and-forget job. Your SPF record does not need maintaining. Your DKIM keys sit there working.
Reputation is not like that. Five reasons we leave warming on permanently.
It stops the decay. Positive signals age out. Go quiet for a month and the record that made your last campaign land is largely gone by the time you send the next one.
It offsets your campaigns. Any bulk send produces negatives. People who do not open, people who delete, the occasional complaint. That is normal and unavoidable even with a good list. Warming runs underneath, feeding in the opposite signals, so the overall balance stays healthy instead of your own campaigns dragging you down over time.
It smooths the spikes. Silence followed by four thousand emails on a Tuesday morning is, from the provider's side, indistinguishable from an account that has been compromised. A constant baseline means your campaign reads as an increase rather than an anomaly.
It keeps you ready. When something comes up and you need to send this week, you can. There is no lead time spent rebuilding first.
It warns you early. Because warming measures continuously, a dip shows on the dashboard before it shows in a campaign result. That is a far cheaper place to find a problem, and it is the difference between slowing down for a fortnight and spending two months in recovery.
It costs nothing extra to leave running. Weighed against a quarter of underperforming sends, it is the cheapest insurance available on the whole operation.
The bit you will actually notice
There is one practical consequence, and it is worth being upfront about because it surprises people.
Once warming is running, you will start receiving emails from people you do not know, and the content will not make much sense. That is the system working exactly as designed. Those are warming messages arriving in your mailbox as part of the network.
Please do not report them as junk or phishing, and do not block the senders. Doing so works directly against what the warming is building, and it is the single most common way a client accidentally undermines their own reputation.
Every warming email carries an identifying code at the bottom so you can recognise them at a glance. We send you your code when your account is connected. It is worth passing that on to anyone else with access to the mailbox, because the person who reports them is usually not the person who read the setup email.
What this looks like day to day
Your domain reputation appears on your dashboard a few days after warming starts, and updates from there. You can see where your mail is landing rather than inferring it from open rates.
We watch it so you do not have to. If it starts to slip, that is our problem to raise with you, along with a recommendation: slow the schedule, clean the list, pause and let it recover. The point of measuring continuously is that the conversation happens before a campaign rather than after one.
What we need from you is small. Authorise the warm-up connection when we send the link. Leave the warming mail alone and tell your team to do the same. And let us know before an unusually large send so we can lift the baseline ahead of it instead of scrambling afterwards.
The rest, the authentication, the compliance settings, the monitoring and the sending schedule, sits with us.
Where this leaves you
Reputation is not a score you earn and keep. It is a rolling judgement, made continuously, by parties you cannot appeal to, about a domain your whole business sends from.
You can either feed that judgement deliberately or leave it to whatever your sending schedule happens to produce. Warming is simply the deliberate version, and running it continuously is the difference between a domain that is an asset and one you have to repair every time you want to use it.
Domain warming is built into every FlipSend account rather than sold as an add-on, along with inbox placement testing, list validation and the rest of the deliverability tooling. Australian owned, Australian hosted, and monitored daily. If you would like us to look at where your domain currently stands, get in touch and we will run the numbers.