Warming up a new sending domain in six weeks

A new domain has no history. Mailbox providers see mail from a name they have never met, and some of them limit how much they accept until you prove people want it. Microsoft’s warmup guidance puts it plainly: it takes four to eight weeks to reach maximum deliverability, depending on target volume and engagement, and longer if recipients do not seem to want the mail.

So you ramp up. The question is how. Most guides give you a table of numbers. We will give you one too, but the numbers are the least important part. What carries the plan is who you send to in each week, and what you do when the feedback turns bad.

What warmup is and is not

Warmup is a sequence of small, well-received sends that lets providers build a picture of you. It is not a trick. Google’s own sender guidance says to start with a low sending volume to engaged users and slowly increase it, and says nothing more specific. There is no official table of daily volumes from Google or Yahoo. Every schedule you read, ours included, is somebody’s experience.

That has a practical consequence. If a schedule says "1,000 on day nine" it cannot be right for everyone, because the real input is how recipients react. Complaints, bounces and deferrals are the dial. The calendar is only a guess about where the dial will let you go.

The flat ladder, and where it breaks

Omnisend publishes a four-week sample: 250 emails a day in week one, 500 in week two, 1,000 in week three and 2,000 in week four, starting with existing subscribers and adding customers and new signups later. It also suggests no more than one campaign a day and three a week. It is a fair outline and easy to follow.

Where it breaks is the flatness. It does not say what to do when week two goes badly. It also tops out at 2,000 a day, which suits a list of a few thousand and leaves a 50,000 contact list with no plan for week five. If you stick to it mechanically, you will either stall or jump. The better habit is to treat the ladder as a ceiling you step toward only when the numbers say go.

Engagement tiers: the part that matters

Microsoft’s guidance gives the clearest tier structure we found. In weeks one and two, send to people who opened or clicked in the past 30 days. In weeks three and four, widen to 60 days. During the first six weeks, do not send to anyone who has not opened or clicked in the past 90 days. When you add an older segment, add it in chunks of about 15 percent of existing volume.

The reasoning is simple. Recent openers rarely complain and rarely bounce, so early reputation data looks good. Old addresses are where spam traps and abandoned mailboxes live. See list hygiene and spam traps for why that matters.

A six-week plan you can copy

Here is the sample ramp for a list of 10,000 contacts who have opened or clicked within the last 90 days. Treat the figures as a starting shape and rewrite them for your list size. The principles are what to keep.

Consistency counts. Microsoft notes that the steadier you are with volume, frequency, complaint and bounce levels the faster you build reputation, and that sending less often than weekly slows it down. So a Tuesday and Thursday rhythm beats one big blast and two weeks of silence.

Mixing in transactional mail

If you already send order confirmations, password resets or receipts, keep sending them. Real, wanted, one-to-one mail is the best reputation signal you have, and it tends to be opened. Whether to send it from the same domain as your marketing is a design choice: shared domains share reputation, which helps early and hurts if marketing goes sideways. We lean toward keeping the domain shared during warmup and splitting only if you have a reason. That is our judgement, not a rule from the sources above.

Mailnaptic offers transactional email on Pro and above, and we have not verified here whether warm-up caps apply to it the same way as to campaigns and automations. The Domains page lists the caps for campaigns and automations. Check what your account shows before you plan around it.

One more caution: do not fake it. Sending marketing mail dressed up as a receipt to build volume is the kind of thing that creates complaints. See our Black Friday sending plan for why warmup should be finished well before a peak.

The feedback you read each week

You need three numbers after every send. Complaints, hard bounces and deferrals or delays.

Expect some turbulence. Microsoft’s guidance says to expect some bulking, meaning mailbox providers filtering your marketing mail as bulk or spam, and some blocking, and that the answer is to keep sending to engaged subscribers rather than stop.

When to slow down

Slow down means repeat last week’s volume and tighten the tier. It does not mean stop. The diagram below is the rule we would follow.

What Mailnaptic warmup does

Once a domain is verified, the Domains page shows a Warm-up status card. Warm-up starts automatically with your first campaign send. The card shows a level from 0 to 10, a health score, and an estimated daily cap for campaigns and automations.

The level labels read roughly like this: Level 1 about 50 a day, Level 2 about 100, Level 3 about 200, Level 4 about 400, Level 5 about 800, Level 6 about 1,600, Level 7 about 3,200, Level 8 about 6,400, Level 9 about 12,800, and Level 10 about 25,600. Each level doubles the one before, up to a platform daily cap that is 50,000 a day by default. Those are estimates in the app, not guarantees. The card also tells you when you are active: if you sent in the last 24 hours it says you advance to the next level in the next warmup cycle, and if you did not it asks you to send a campaign today.

Two things we want you to understand. First, the cap is a ceiling, not a recommended schedule. The tiers in this article decide who you send to; the cap only prevents you from going too fast. Second, the health score moves the cap. Per the interface, the score comes from bounce rate, complaint rate and open engagement, with 70 and above healthy, 40 to 69 fair, and below 40 possibly pausing progression. Below 80 you get a recovery plan button.

Why every schedule is a heuristic

No provider publishes the rules. Google says gradual and engaged. Yahoo says nothing on ramps. Microsoft gives windows and 15 percent steps. M3AAWG’s published documents list sender best practices and no warmup table that we could find. Everything else is vendor experience, including the sample numbers on this page.

Three things change the real answer. Your list source: Microsoft’s guidance puts opt-ins first, and mail to people who did not clearly ask for it takes longer to warm, if it warms at all. Your cadence: weekly or better. And your engagement: a list where most people open warms differently from one where few do. Use the schedule to plan, and the feedback to decide.

And if you must send a big campaign before week six? Send to your most engaged group only and wait. A smaller campaign that lands well is worth more than a full one that goes to spam. Silent subscribers can be handled later with a win-back campaign.

For the wider picture of what a small sender should do in its first month, see our 30 day plan for a small business. For the rules the major providers enforce, see Gmail and Yahoo sender requirements.