Nobody trusts your new domain

How to warm up a fresh sending domain, the practices that actually build reputation, and the exact allowances 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.

Mailbox providers keep score per sending domain; Gmail tracks volume, feedback and limits per domain and per IP address, and a newly registered domain starts with no score at all. Warmup is how you earn one: start small, send mail people actually want, and grow volume as providers accumulate evidence that you are a business and not a burner. Early mistakes are expensive, because Gmail is explicit that improvements take time to show up in how your mail is classified.

Nitrosend enforces a daily allowance from the first send, and the exact numbers are below. But an allowance 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

Send marketing from a subdomain such as send.yourdomain.com, not your bare apex domain. M3AAWG, the industry's anti-abuse working group, strongly recommends a separate subdomain for each sending purpose, and Yahoo notes that each DKIM domain carries its own reputation. The separation keeps a rough campaign away from the domain your team's everyday inboxes depend on. It is not a clean slate: Gmail counts a subdomain's volume toward its parent domain, and M3AAWG still recommends warming a new subdomain when the parent is established. The setup is covered end to end in our sending domains guide.

No domain ready yet? Every brand can activate a protected <brand>.nitrosend.net sender instead, on a shared root Nitrosend has already verified, so there is no DNS to touch. A domain you own is still the better long-term home: its reputation belongs to you, and a verified custom domain counts toward your standing on Nitrosend, which the hosted sender does not.

Authentication comes with verification. A custom domain verifies on Nitrosend with SPF, DKIM, a custom return path and a DMARC record, so every send is authenticated from the first message. DMARC can start at p=none; any valid policy passes. None of this is optional any more. Since February 2024, Gmail has required anyone sending close to 5,000 messages a day to personal Gmail accounts to pass SPF and DKIM, publish a DMARC record, keep the From domain aligned with SPF or DKIM, and offer one-click unsubscribe on marketing mail. Yahoo set similar rules without naming a volume threshold, and Outlook.com has required SPF, DKIM and DMARC from domains sending over 5,000 a day to its consumer addresses since May 2025. Enforcement has teeth: since November 2025 Gmail has been ramping up temporary and permanent rejections of non-compliant mail, and Outlook.com rejects it with a 550 5.7.515 error.

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. Gmail's own advice to a new sender is to start with a low volume to engaged users and increase slowly.

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.

Never point a purchased or long-dormant list at a fresh domain. Gmail says it plainly: don't purchase email addresses. Stale lists bounce, and a new domain has no history to absorb it. If an older list is all you have, verify it first: in Contacts, Verify list checks every address against a prepaid quote, and a list that comes back clean counts toward your standing. Verification removes dead addresses; it never creates consent.

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 burst that fills the allowance reads as a script. Gmail asks senders to send at a consistent rate and avoid bursts, and notes that volume can grow faster when you send daily rather than weekly. M3AAWG's sender best practices put an average warmup at about six weeks.

Consistency matters after warmup too. M3AAWG warns that lapses in sending affect both forming and sustaining a reputation, and a domain that goes quiet for months has less recent evidence working for it. Warmup assumes regular sending afterward.

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:

Stops also need a minimum count of events, ten hard bounces or three complaints (ten complaints for an account), so a single unlucky address never stops a send. A campaign is judged on its own send, a flow on its last 24 hours, and an account on its last day and week. For calibration, Gmail asks senders to keep the spam rate reported in Postmaster Tools below 0.1% and never reach 0.3%. Mailbox providers publish no bounce threshold. The warning line sits inside those limits deliberately, so a problem surfaces while it is still a list-cleaning job rather than weeks of provider-side repair.

Watch Gmail's side of the ledger too. Verify the domain in Google Postmaster Tools on day one: its compliance status dashboard shows whether you meet Gmail's sender requirements, and its spam rate is the number those lines refer to. Expect gaps early; Google notes data can be missing on days when volume is too low.

Nitrosend suppresses an address after a hard bounce, a spam complaint, or three soft bounces, and a suppressed address receives no further email of any kind from the account. 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 one-click unsubscribe headers and an unsubscribe link in its footer. Google observes that unwanted messages without one-click unsubscribe are more likely to be reported as spam, and that complaint costs far more than the unsubscribe would have.

What Nitrosend enforces

From the first send, every account works inside a daily allowance: recipients per rolling 24 hours, set by your plan and your sender standing. This is the actual table the system reads:

Enterprise allowances are set by contract. The allowance is account-wide, across every brand and sender, and it counts everything: campaigns, flows and transactional mail.

Standing is not a calendar, and there is no day on which the limits step up by themselves. The account is re-ranked every hour, and again after every hard bounce or complaint, from evidence that means something to a mailbox provider: a verified custom domain and its strength and age, a list that verifies clean, an audience connected from your previous provider with its engagement history, clean sending history on Nitrosend, and account signals such as age and a settled payment. Strong evidence can earn Standard or Trusted on day one, and a list that verifies clean is the most direct route. Payment alone never does. A Trusted account drops back to Standard when its last seven days cross a warning line, and a critical breach quarantines any account.

That makes the allowance a ceiling, not a warmup schedule. Probation retains stricter content checks and a one-time bulk observation: up to 100 recipients in the first two minutes, then automatic continuation unless an existing safety control intervenes. Missing delivery receipts do not extend that wait. Individual transactional mail does not wait behind bulk. A Starter account that earns Trusted on its first day has the full 100,000 allowance, but Gmail may still have never heard of its domain.

Four behaviors worth knowing before you plan a send:

Big campaigns send in batches. A campaign larger than your remaining allowance still schedules. The recipients that fit go now and the rest wait for capacity to return, and the warning says so before you schedule: This campaign will send in batches. Upgrading wakes the waiting send.

Transactional mail shares the allowance. Receipts, password resets and magic links count against the same rolling allowance, so budget campaigns below the limit, not to it. When the allowance is exhausted, the API returns a 503 with a Retry-After header and a retry_at time; retry then with the same idempotency key.

New content is checked. On Probation, every new piece of content is reviewed before it sends. On Standard and Trusted, a new sender's first content is reviewed, and on Standard so is its first campaign to 500 or more recipients.

Your agent can always see your position. Allowance and pacing ship in the standard status surface, so anything driving Nitrosend over MCP reads them from nitro_get_status (and anything else from GET /v1/my/delivery/status). Trimmed to the fields that matter here:

"delivery": {
  "assessment_scope": "account_capacity",
  "admission_status": "allowed",
  "commercial_capacity": {
    "status": "known",
    "limit": 10000,
    "reserved": 0,
    "accepted": 320,
    "provider_unknown": 0,
    "remaining": 9680,
    "source": "plan"
  },
  "pacing_state": {
    "status": "ready",
    "policy_version": "delivery-pacing-v3",
    "queued_quantity": 0
  },
  "issues": [],
  "observed_at": "2026-09-29T09:00:00.000000Z"
}

Check commercial_capacity.remaining before sizing an audience.

A worked example: 30,000 contacts on Starter

Say you verified send.yourdomain.com this morning, you are on Starter, and you have a 30,000-contact list sorted by engagement. Probation has 10,000 recipients per rolling 24 hours, with the one-time initial bulk check described above. Strong positive list evidence can earn Trusted on the same day, giving the full 100,000 allowance. Monthly email credits and safety checks still apply. Permission to send is not a recommendation to send the whole list at once. A conservative schedule could look like this:

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 allowance counts everything the account sends that day, so leave headroom under it for flows and transactional mail; 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.

Standing belongs to the account; reputation belongs to the domain. Your allowance and standing apply across every brand and sender on the account. Mailbox providers see it differently: they score each domain on its own record. Add a second domain to an established account and it gets the account's allowance, not the old domain's history with Gmail, so warm it the same way.

Bringing your own keys changes nothing. Send through your own SES or SendGrid credentials and the allowance, standing, suppression and review still apply, 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 provider manages the IP side of reputation.

Three separate systems. The allowance caps how many recipients the account reaches in a rolling day. Pacing spreads admitted mail over time, faster as standing rises, per mailbox provider, and backs off when a provider pushes back. Feedback enforcement watches bounces and complaints on every campaign, flow and account, and stops a send whose numbers go bad, whatever the allowance says. They are deliberately independent: a Trusted account with one bad campaign gets that campaign stopped even though the allowance had room. The admission and pacing model behind them is in the scale write-up.

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. The allowance will not react; it follows plan and standing, not outcomes. Feedback enforcement is what reacts. Past 1.5% you are warned. A campaign past 5% over 500 sends, or 10% early, is paused, and an account past 5% across 500 sends is quarantined and its sending stops until a review. A Trusted account whose last seven days cross a warning line drops to Standard.

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. A paused campaign does not resume on its own; clean the list and send it again. A quarantined account returns to Probation after a 14-day cooldown of clean or no sending, and a human review lifts the suspension.

The wrong move is pushing through it: every further send into a bouncing list converts allowance 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 how their filters weigh the evidence. 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.

Common questions

Close

Warmup on Nitrosend is enforced, visible, and published: the allowances are in the table above, the remaining budget is one status call away, and a Probation account cannot blast a cold list. The part that stays yours is the sending itself: mail people asked for, to addresses that exist, at a steady pace, well under the ceiling at first. Shorter reference answers on warmup and its neighbors are collected in the deliverability reference.

Do that for a few weeks and the providers stop treating you as a stranger. A domain warmed properly this month is still an asset in five years, as long as the sending stays that way.

Starting on a fresh domain? Verify it today and start with your most engaged contacts. Start free, or reach out if you're migrating real volume and want a warmup plan mapped to your list.