Spam placement only ever slows a mailbox down
At 10% spam a mailbox goes on watch and sends a little slower. At 20% warmup and cold sending both drop to half volume, and they return to normal on their own once placement recovers.
Email · Warmup
A slow, careful ramp for every new mailbox.
Each mailbox trades a little ordinary email with the other mailboxes on your instance, starting at 10 a day and adding one a day up to 40. It watches where that mail lands and slows a mailbox down the moment placement slips.
The ramp. Ten a day, one more each day, never past forty.
Each mailbox follows its own ramp, spread across the warmup hours you set for it. The real number can come in lower than the ramp: a mailbox never writes to the same partner twice in a day, and its target is capped by how many partners are free.
If a warmup email lands in spam at Gmail, Outlook or Yahoo, the ramp stops climbing at once: today's target drops by a quarter for 48 hours and the daily increase pauses for three days, without catching up afterwards.
Read about the rampWhat warmup mail is. Plain-text threads that read like real mail.
Each message is plain text with no tracking pixel, on everyday topics that vary in tone and length, and conversations rotate so the same mailbox rarely gets the same one twice. Partners write back on their own schedule, about three times in ten by default, and each thread closes after a few turns.
A token for one inbox
Every warmup email carries a single-use token bound to the inbox it was sent to. It proves the copy arrived and records where it landed, then it is spent. Replayed or forwarded anywhere else, it counts for nothing.
Out of your way
By default, warmup mail in and out is filed into its own folder, so it never buries your inbox or your Sent folder. It never shows up in the unified inbox either.
Cleaned up for you
Warmup mail is deleted after 30 days by default. Set a shorter or longer window per mailbox, down to three days.
Health. Landing in spam slows a mailbox down. Hurting other people takes it out.
Placement is judged at Gmail, Outlook and Yahoo once a mailbox has 20 verified deliveries in a week. Complaint and bounce lines sit below the ones Google and Amazon SES enforce, so a mailbox is held back before a provider has to act.
Complaints and bounces take it out of the pool
Complaints at 0.10% or bounces at 5% take a mailbox out for 7 days and pause its cold sending; 0.30% or 10% take it out for 30. The standing follows the address, so reconnecting it does not reset anything.
Your own pool. Warmup happens among the mailboxes you run.
Every instance has its warmup pools from the first mailbox, and its mailboxes write to each other. Each draw favours the inbox that is owed the most mail, and no inbox receives more than about twice what it sends in a day.
A small pool gives you fewer, narrower readings. Warmup traffic is automated and is not the same as people engaging with your mail, so treat what it shows as a signal, not a verdict.
10
emails on day one
+1
each day after
40
a day at most
30
days before warmup mail is deleted
Every default can be changed per mailbox.
Questions. Warmup, answered.
For the whole picture, read the warmup guide.
How long does warmup take?
Plan on three to six weeks. At the default ramp a mailbox reaches 40 emails a day after about a month. Warmup is evidence about how providers treat a mailbox, not a guarantee of where its mail lands.
Should warmup keep running once my campaigns start?
Yes. Warmup runs alongside cold sending at up to five messages a day, so a change in how providers treat a mailbox shows up in its warmup numbers, and its health bands slow it down when placement slips.
What gets a mailbox taken out of warmup?
High complaint or bounce rates: 0.10% complaints or 5% bounces pause it for 7 days, 0.30% or 10% for 30. Spam placement on its own never removes a mailbox; it only slows warmup down until placement recovers.
Who does my mailbox warm with?
With the other mailboxes on your instance. A handful of mailboxes makes a small pool, and a small pool tells you less about how the wider world treats you. Mailboxes at providers that filter on sender reputation give the most useful readings.
Which providers does placement count at?
Gmail, Outlook and Yahoo. They filter on sender reputation, which is what cold email is judged on. Smaller mail hosts run their own filters, so their spam folder is never held against you.
Does it need a hosted service?
No. Warmup runs on your instance with its built-in library of hand-written threads, and works with no AI provider at all.
What this is not
Warmup is not a deliverability guarantee. It does not promise inbox placement or a better reputation, and it is not a way to disguise automated traffic. It helps you follow provider rules and see trouble early.
Warm your mailboxes on your own instance.
Connect Google, Microsoft or any SMTP and IMAP mailbox, then switch warmup on from the mailbox's Warmup tab.