Email warmup planner
Set your target daily volume, mailbox count and domain state and get the day-by-day sigmoid ramp schedule — safe sends per mailbox, the fleet total, and the day you reach full capacity. Free, private, no signup.
The domain already has a sending history at the mailbox providers, so the standard ramp applies.
The curve is the smoothstep sigmoid t² × (3 − 2t) where t = day ÷ ramp length — the same one Autocloz enforces on a warming mailbox. It is deliberately not linear: a straight line from 0 to your target is the pattern spam filters recognise. 100% client-side; nothing you type leaves your browser.
- Ramp length applied21 days
- Day the fleet reaches full capacityDay 21
- Day 1 sends per mailbox1
- Total sent across the whole ramp2,205
- Per mailbox across the whole ramp441
- Mailboxes needed for 500/day13
- First day the fleet clears 500/dayNot on this plan
Autocloz runs this ramp for you on every connected mailbox — the sigmoid, the daily ceiling and the bounce-rate auto-pause are built in, not a spreadsheet you have to police.
Warm mailboxes automatically — start freeWeek by week
Day-by-day warmup schedule
| Day | Per mailbox | Fleet (5 mailboxes) | % of target |
|---|---|---|---|
| 1 | 1 | 5 | 3% |
| 2 | 1 | 5 | 3% |
| 3 | 2 | 10 | 5% |
| 4 | 4 | 20 | 10% |
| 5 | 6 | 30 | 15% |
| 6 | 8 | 40 | 20% |
| 7 | 10 | 50 | 25% |
| 8 | 13 | 65 | 33% |
| 9 | 16 | 80 | 40% |
| 10 | 19 | 95 | 48% |
| 11 | 21 | 105 | 53% |
| 12 | 24 | 120 | 60% |
| 13 | 27 | 135 | 68% |
| 14 | 30 | 150 | 75% |
| 15 | 32 | 160 | 80% |
| 16 | 34 | 170 | 85% |
| 17 | 36 | 180 | 90% |
| 18 | 38 | 190 | 95% |
| 19 | 39 | 195 | 98% |
| 20 | 40 | 200 | 100% |
| 21 | 40 | 200 | 100% |
This is a plan, not a promise. Warmup shapes volume; it cannot fix a bad list, missing authentication or a domain that has already been burned. Treat the numbers as a safe upper bound to ramp toward, and slow down the moment placement or bounce rate moves against you.
Guardrails to run alongside the ramp
- At 40 per mailbox you need 13 mailboxes to reach 500 a day. You have 5, so this fleet plateaus at 200 a day.
- Warmup counts toward the same daily ceiling as campaigns. In Autocloz, warmup traffic is not added on top of your campaign volume — it is drawn from the same per-mailbox cap, so a warming mailbox can never push a domain past a safe send rate. If you plan warmup and campaign volume as two separate budgets, you will double the real load on the domain.
- Auto-pause on a bounce-rate spike. Autocloz pauses a mailbox when its bounce rate over the recent window crosses 2.5%. Whatever tool you use, set a hard stop in that region: a ramp that keeps climbing through a bounce spike is how a domain gets burned in a week.
- Measure placement, not acceptance. A 250 OK is not an inbox. Autocloz runs weekly inbox-placement seed tests against real Gmail, Outlook and Yahoo mailboxes and reports the actual folder — inbox, promotions, spam or missing. If a ramp looks healthy on acceptance but placement is drifting to spam, hold the volume where it is.
- Authentication and one-click unsubscribe first. SPF, DKIM and DMARC should be live and monitored before day 1 — use the SPF, DKIM and DMARC generator if they are not. Every Autocloz mailbox also injects RFC 8058 one-click unsubscribe automatically, which Gmail and Yahoo now expect from bulk senders.
See how Autocloz runs this automatically on inbox warmup, or self-audit the rest of your setup with the email deliverability checker.
The curve behind the schedule
No rule of thumb and no lookup table is involved. Each day's figure comes from a smoothstep: divide the day number by the ramp length to get a fraction between zero and one, pass it through t squared multiplied by three minus twice t, and scale the result by your target. A floor of a single send stops day one ever landing on zero.
Three properties fall out of that formula, and they are what make the table worth planning against. The output never rises above the target you set, the final day of the ramp lands exactly on it, and the sequence only ever climbs — so the first day your fleet clears a volume goal is one definite answer rather than an estimate.
The shape matters more than the arithmetic. A straight line adds an identical increment every single day, which is a signature no human mailbox produces. The S-curve stays nearly flat through the opening days, does most of its climbing in the middle, and eases into a plateau. This is the same curve Autocloz enforces on a warming mailbox in production, not a marketing approximation of it.
What each of the five inputs moves
Target sends per mailbox per day sets the plateau, the number the curve converges on and then holds. Mailbox count multiplies that into fleet capacity and never alters the per-mailbox shape. Ramp length is simply how many days the same climb is spread over. The daily volume you need is not used to draw the schedule at all — it is compared against it, which is how the panel can name the mailbox count your goal requires and the first day the fleet gets there.
Read the results panel from the top down. Plateau capacity answers what this fleet can do once warm, the ramp totals answer how much sending getting there involves, and the goal row answers when. If that row reports the goal is unreachable, the answer is more mailboxes rather than a higher per-mailbox ceiling, and the panel spells out the number required at your current rate.
How the domain-state control changes the plan
This control is a planning guideline, not a product feature. Nothing here inspects your registration date and Autocloz does not read domain age either. What the setting does is stretch the identical curve across more days, so a colder domain gets a gentler slope rather than a different plan, and the panel tells you when the length you typed has been extended.
- Established, months of sending behind it
- The ramp runs at exactly the length you entered. Providers already hold a history for the domain, so the climb has something underneath it from the first day.
- Recently authenticated
- The ramp is extended by a quarter. Records are live but almost no behaviour sits behind them yet, so the same climb is spread thinner across more days.
- Brand-new domain
- The ramp is extended by half. With no history at all this is the riskiest starting point, and the extra days keep the opening week in single figures.
Where warmup plans usually go wrong
The most common error is budgeting warmup and campaign traffic as two separate allowances. In Autocloz they draw from the same per-mailbox ceiling, so treating them separately doubles the real load the domain carries. Whatever tool you use, plan one number per mailbox per day and let every kind of send come out of it.
The second is raising the per-mailbox target instead of adding mailboxes. Past fifty a day on cold traffic this planner raises a caution for a reason: that ceiling reflects how the receiving providers behave, and it does not move because your quota did. A ramp shorter than a fortnight draws its own caution — the curve still opens gently, but the mailbox gets less time to build a track record before it arrives at full volume.
The third is reading the table as a promise. It shapes volume and nothing else. Dead addresses, records that were never published and a domain already carrying damage all sit outside what any ramp can repair, and the figures to watch as you climb are bounce rate and the folder your mail actually lands in — not whether the receiving server accepted the message.
Email warmup FAQ
Is the email warmup planner free?
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Yes — free, no signup, 100% client-side. Every number is computed in your browser and nothing you type is sent anywhere.
How long should an email warmup take?
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21 days is the default this planner uses, and it is the ramp length Autocloz applies to a new mailbox. Shorter ramps are possible but leave the provider less time to build a reputation for the mailbox; a domain with no sending history is safer stretched to 4-5 weeks. Warmup is not a one-off either — you keep the volume ceiling and the monitoring in place after the ramp ends.
Why is the ramp a sigmoid instead of a straight line?
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A linear ramp is a machine-recognisable pattern: the same increment every day, forever. A sigmoid — the smoothstep curve t squared times (3 minus 2t) used here — starts almost flat, accelerates through the middle, then flattens into a plateau, which is how a real mailbox's volume grows. Autocloz enforces exactly this curve on every warming mailbox.
How many emails a day can one mailbox safely send?
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There is no official number and it depends on the provider, the domain's history and how your recipients react. For cold outreach, keeping each mailbox under roughly 50 a day and adding mailboxes to reach your volume is the conservative approach — that is the ceiling above which this planner raises a caution.
Does hitting these numbers guarantee inbox placement?
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No. This is a planner, not a promise. A ramp shapes volume; it cannot fix an unverified list, missing SPF, DKIM or DMARC, or a domain that has already been burned. Measure real folder placement with seed tests and slow the ramp the moment placement or bounce rate moves against you.
Related: inbox warmup, SPF, DKIM and DMARC generator, email deliverability checker, send-time calculator.
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Stop running the ramp by hand.
Autocloz applies this sigmoid to every connected mailbox automatically, runs weekly inbox-placement seed tests, and auto-pauses on a bounce-rate spike.