Nobody trusts your new domain

How to warm up a fresh sending domain, the practices that actually build reputation, and the exact caps we enforce while you do it.

Gmail has never heard of your domain. Neither has Outlook, or Yahoo, or any of the filters that decide whether your email lands in an inbox or evaporates. To them, a domain that verified this morning and is already sending thousands of messages looks exactly like what it usually is: a spammer who just spun up infrastructure, will burn the domain in a week, and will register another one when it dies.

Everything a mailbox provider knows about you is attached to your sending domain, and a new domain knows nothing about you either. Warmup is how you fix that: start small, send mail people actually want, and grow volume as providers accumulate evidence that you are a business and not a burner. The first few weeks of a domain's life decide its default treatment for a long time afterward.

Nitrosend enforces the ramp automatically, and the exact numbers are below. But the ramp only controls how much you send. Whether the reputation you build is worth having comes down to who you send to and what they do with it, and that part no platform can automate for you.

Send from a subdomain, and get the plumbing right

Warm up send.yourdomain.com, never your bare apex domain. The subdomain isolates your marketing reputation from the domain your team's everyday inboxes run on, so a rough campaign can never drag down the mail your company actually depends on. This is the setup providers expect from senders, and it is covered end to end in our sending domains guide.

Authentication comes with verification. When a domain verifies on Nitrosend, its SPF, DKIM, and return-path records are part of that verification, so every warmup send goes out fully authenticated from the first message. This stopped being best practice and became a requirement in February 2024, when Gmail and Yahoo began demanding SPF, DKIM, DMARC, and one-click unsubscribe from anyone sending at volume; unauthenticated bulk mail is now rejected outright rather than filtered.

Start with the people who asked

Providers watch a young domain's mail closely, and thin history means every signal counts double: opens and replies build trust, while bounces and spam complaints destroy it faster than anything else.

Your most engaged contacts are the warmup audience. Recent signups, recent openers, recent buyers. Send to the segment that is most likely to open and least likely to complain, and widen from there as the caps rise.

Never point a purchased or long-dormant list at a fresh domain. Stale lists bounce, and bounce rate is the single fastest way to burn a new domain. The long tail of your audience can wait until the domain has history, and the dead addresses in it should be cleaned out rather than mailed.

Send your real mail. The newsletter people signed up for, the onboarding sequence they triggered. Content invented purely "to warm up" trains recipients to ignore you, and that disengagement feeds the same metrics you are trying to build.

Grow steadily, then keep going

A domain sending 40, 60, 80, 120 messages across its first week reads as a company finding its footing. Six days of silence followed by a cap-filling burst reads as a script. Spread your sending across the ramp rather than hoarding budget for the day the limit rises.

Consistency matters after warmup too. Long gaps early in a domain's life throw away the impression you paid for, and providers discount history that ends abruptly. Warmup assumes regular sending afterward; a domain that goes quiet for months starts drifting back toward unknown.

Watch two numbers like production metrics

After every meaningful send in the first weeks, look at your delivery insights and check bounce rate and spam complaints. Those two numbers are how mailbox providers score you, and they are how we score you too. These are the actual thresholds the system holds every sender to, over a trailing seven-day window:

Standing	Bounce rate	Complaint rate
Healthy, reputation graduates	under 1.5%	under 0.05%
Warning	2.5%	0.1%
Critical	5%	0.5%
Sending silenced	10%	1%

Earning trusted standing is stricter again: bounce under 0.5% and complaints under 0.02%, sustained over thirty days. For calibration, Gmail's published ceiling for bulk senders is a 0.3% complaint rate, with 0.1% as the working target. The thresholds sit inside the providers' lines deliberately, so a problem surfaces while it is still a list-cleaning job rather than weeks of provider-side repair.

Nitrosend suppresses hard bounces and unsubscribes automatically, so no bad address is ever hit twice. The first hit still counts against you with the provider, which is why the clean list going in beats the suppression catching it after.

And make leaving easy. Every marketing email sent through Nitrosend carries an unsubscribe link; a recipient who cannot find the way out reaches for the spam button instead, and that complaint costs far more than the unsubscribe would have.

What Nitrosend automates

From the moment your domain verifies, every send is held to a daily cap that rises as the domain ages. This is the actual table the system reads, per plan tier:

Domain age	Free	Paid	Trusted
0 to 3 days	50/day	1,000/day	5,000/day
4 to 7 days	100/day	3,000/day	15,000/day
8 to 14 days	250/day	10,000/day	50,000/day
15 to 21 days	500/day	30,000/day	Unlimited
22 to 35 days	1,000/day	Unlimited	Unlimited
36+ days	Unlimited	Unlimited	Unlimited

The caps are a step function, not a gradual slope; the same schedule as a shape:

sends/day on the paid plan

unlimited                                     +--------------->
   30,000                            +--------+
   10,000                   +--------+
    3,000          +--------+
    1,000 +--------+
          day 0    4        8        15       22

There is nothing to configure and nothing to graduate. Send within the budget and the limits raise themselves; past the ramp they lift entirely and sending is bounded only by your plan.

Three behaviours worth knowing before you plan a send:

Campaigns are all-or-nothing. An audience larger than today's remaining budget blocks the send; nothing partial goes out. Trim the audience or schedule it for tomorrow. You never have to work out which half of an audience actually received the email.

Transactional email is never held. Receipts, password resets, magic links: they go out regardless of warmup, because the recipient asked for them and providers treat them accordingly.

Your agent can always see your position. The warmup state ships in the standard status surface, so anything driving Nitrosend over MCP reads it from nitro_get_status:

"warmup": {
  "active": true,
  "domain_age_days": 4,
  "daily_limit": 100,
  "sends_today": 32,
  "remaining_today": 68
}

Check remaining_today before sizing an audience.

A worked example: 30,000 contacts on the paid plan

The table above is policy; here is what it looks like as a plan. Say you verified send.yourdomain.com this morning, you are on a paid plan, and you have a 30,000-contact list sorted by engagement. The ramp maps onto it like this:

Days	Cap	What to send
1 to 3	1,000/day	Your 1,000 most engaged contacts: recent buyers, recent openers. Flows on from day one.
4 to 7	3,000/day	The regular newsletter to your top 3,000.
8 to 14	10,000/day	Campaigns to the top third of the list, widening the ring each send.
15 to 21	30,000/day	The first full-list campaign, now backed by two weeks of clean history.
22+	Unlimited	Normal operation.

Each stage widens the audience one ring at a time, so by the day the whole list gets mailed, providers have three weeks of evidence that your mail gets opened. Two practical notes: the cap counts everything the brand sends that day, so leave headroom under it for flows and transactional mail rather than budgeting campaigns to the exact limit; and if a stage shows rising bounces, hold at that ring and clean before widening; falling a few days behind the schedule costs nothing.

How the system actually works

A few details of the implementation matter to how you plan.

The clock starts at verification. Domain age is measured from the moment the domain verified, not from account creation and not from your first send. Verifying the domain early and starting small immediately is free ramp progress. Re-verification never resets it; DNS hiccups and automatic re-checks keep the original date.

Warmup follows the domain, and the newest domain wins. Each sending domain carries its own age. Add a second domain to an established brand and that new domain runs its own ramp from day zero while the old one keeps its full limits, so route the new domain's mail accordingly rather than assuming the brand's history transfers; mailbox providers score each domain on its own record.

Bringing your own keys changes nothing. Send through your own SES or SendGrid credentials and the ramp still applies, because the thing being warmed is your domain's reputation with Gmail and Outlook, not the infrastructure behind the send. The same boundary separates domain warmup from IP warming, which only applies to dedicated IPs; on shared infrastructure the IP side of reputation is managed for you.

Warmup is one of three separate systems. Warmup caps daily volume by domain age. Pacing spreads a cleared send into blocks with pauses, sized by how much trust the account has earned. And deliverability monitoring watches bounce and complaint rates on every domain, throttling or holding sends when a domain's health slips, whatever its age. They are deliberately independent: a mature domain with a bad week gets held by health monitoring even though warmup cleared it long ago. The pacing ladder and the throughput behind it are published in the scale write-up.

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When it goes wrong anyway

Say it is day ten, the ramp has been clean, and then a segment you believed was fine starts bouncing. Warmup will not react; it is a function of domain age, not outcomes, and the cap will keep stepping up on schedule. The health system is what reacts. Bounce and complaint rates are tracked continuously on every sending domain, and when they cross the lines in the table above, your standing degrades: pacing slows, alerts fire, and at the extremes sending is silenced entirely, whatever the warmup table would otherwise allow.

What to do about it is unglamorous. Stop sending. Find where the bad addresses came from, an old import or a segment that was never as engaged as it looked, and cut that source, not just the addresses that already bounced. Then resume with your tightest engaged ring, as if the ramp had restarted even though it has not. The rates are trailing windows, so a stretch of clean sending ages the spike out of the data; a silenced sender comes back through a cooldown and a run of demonstrably clean mail.

The wrong move is pushing through it: every further send into a bouncing list converts warmup budget into reputation damage while providers are watching most closely.

What warmup cannot do

The ramp lowers the odds of a reputation problem. It does not remove it, and nothing can, because the receiving providers get the final vote and they do not publish their rules. Warmup is the discipline of giving them only good evidence while they are forming an opinion. A well-paced ramp cannot fix a bad list or unwanted content.

The ramp is also only the start. The habits that carry a domain through warmup, an engaged audience, steady volume, and a clean list, are the same ones that keep it in the inbox for years, and a mature domain can still be burned by one bad send to one bad list.

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Common questions

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Close

Warmup on Nitrosend is enforced, visible, and published: the caps are in the table above, the remaining budget is one status call away, and the ramp makes a day-one blast impossible. The part that stays yours is the sending itself: mail people asked for, to addresses that exist, at a steady pace. Shorter reference answers on warmup and its neighbours are collected in the deliverability reference.

Do that for a few weeks and the caps lift on their own. A domain warmed properly this month is still landing in the inbox in five years.

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Starting on a fresh domain? Verify it today and the clock starts now. Start free, or reach out if you're migrating real volume and want a warmup plan mapped to your list.