Inbox warmup
21-day sigmoid ramp + seed-test placement so your inbox stays out of spam.
Inbox warmup gives every new mailbox an automatic send-volume plan shaped as a sigmoid curve — slow start, controlled ramp, plateau at your target volume — instead of a ramp somebody has to remember to raise. Seed tests run on demand against Gmail, Outlook and Yahoo, so spam-folder slip shows up as it begins rather than a month later.
- ·Sigmoid 21-day ramp curve (not linear)
- ·Inbox-placement probes against Gmail / Outlook / Yahoo
- ·DMARC + SPF + DKIM auto-monitor
- ·Auto-pause on bounce-rate spike
- ·Per-mailbox health score visible at a glance
The detail.
A curve, not a step function
Linear ramps trigger spam filters. Autocloz uses a sigmoid that mimics organic mailbox growth — gentle for the first 5 days, ramp through days 6-15, plateau by day 21. The math is built in; you just enable warmup.
Placement, not just acceptance
A 250 OK from Gmail doesn't mean inbox. Our seed-test probes mail real monitored mailboxes across providers and report which folder the message actually landed in — inbox, promotions, spam, or missing.
Specific to this feature.
How long does email warmup take?
+
21 days by default, which is the ramp length Autocloz applies to a newly connected mailbox. The length is configurable, and a domain with no sending history is safer stretched to four or five weeks. Warmup is not a one-off event either — the daily ceiling, the placement tests and the bounce monitoring stay in place after the ramp reaches its plateau.
Why is the ramp a sigmoid rather than a straight line?
+
A linear ramp adds the same number of messages every day forever, which is a shape no human mailbox ever traces. Autocloz uses the smoothstep curve t squared times (3 minus 2t), where t is the day divided by the ramp length: almost flat for the first few days, steepest through the middle, then flattening into your target. That is how a real mailbox's volume grows as someone starts using it.
How many emails does a mailbox send on day one?
+
Whatever the curve gives, with a floor of one — the ramp value is never rounded down to zero. On a 21-day ramp to 40 sends a day, day one is a single-digit number and the mailbox does not approach its target until the second half of the ramp. You can see the exact day-by-day schedule for your own numbers in the free email warmup planner under Tools.
Does warmup volume use up my campaign sending limit?
+
Warmup sends count against the same per-mailbox daily ceiling as campaign sends. That is deliberate: it means a mailbox that is still warming cannot quietly push a domain past a safe total rate by sending warmup traffic on top of a full campaign quota.
What happens if deliverability slips during the ramp?
+
Two mechanisms watch for it. On-demand inbox-placement seed tests mail monitored Gmail, Outlook and Yahoo mailboxes and report the folder each message actually reached — inbox, promotions, spam or missing — because a 250 OK from the receiving server means accepted, not delivered. Separately, a mailbox whose bounce rate spikes past your threshold that day is auto-paused rather than left to burn the domain.
Can warmup fix a domain that is already burned?
+
No, and it is worth being blunt about that. A ramp shapes volume; it cannot repair missing or misaligned SPF, DKIM and DMARC, an unverified list that generates hard bounces, or a domain that has already accumulated a poor reputation. Warmup is the thing you do so those problems never start, not the remedy once they have.
The full story.
Email warmup exists because mailbox providers score how human a sending pattern looks. A brand-new mailbox that sends one message on Monday and four hundred on Tuesday is not behaving like a person who just started a job, and the classifier that decides inbox versus spam treats it accordingly. The fix is not a trick — it is sending a small, growing, plausible volume for long enough that the provider builds a reputation for the address and the domain behind it.
The shape of that growth matters as much as the destination. Autocloz ramps on a smoothstep sigmoid rather than a straight line: gentle for the first few days, steepest through the middle of the ramp, then flattening into your configured target. A linear ramp is a machine-recognisable pattern because the increment never changes; a sigmoid is the curve a real mailbox traces as someone's work picks up. The same curve runs on every warming mailbox automatically, so there is no spreadsheet to police and no daily limit for someone to forget to raise.
Acceptance and placement are different measurements, and only one of them answers your question. The 250 OK at the end of a successful SMTP transaction means the receiving server took the message, not that a human will see it — the folder decision happens afterwards, in a separate classifier. Autocloz runs on-demand inbox-placement seed tests against monitored Gmail, Outlook and Yahoo mailboxes and reports which folder each probe actually landed in, which is how a mailbox quietly drifting into promotions shows up while its open rate still looks healthy.
If you want to plan the ramp before you connect anything, the free email warmup planner under Tools runs the exact production curve in your browser: enter your target sends per mailbox, your fleet size and your ramp length and it returns the day-by-day schedule, the day the fleet reaches full capacity, and how many mailboxes a given daily volume actually requires. It is a planner rather than a promise — no ramp compensates for an unverified list or broken authentication — but it makes the tradeoff between fleet size, ramp length and time-to-volume concrete before you commit to it.
Try it free.
No credit card. Every feature on this page included.