Almost every founder who asks us about cold email wants to know the same thing: when can we start sending? The honest answer is not today, and not this week. A brand new sending domain has no reputation with the inbox providers, and if you point a few hundred cold messages at it on day one, you will land in spam and stay there. Warmup is the unglamorous step that decides whether your campaign reaches an inbox or a junk folder, and it usually takes 2 to 4 weeks before the domain is ready to carry real volume.
Why a new domain cannot send on day one
When you register a fresh domain and create mailboxes on it, Google and Microsoft have never seen mail from that address. They have no history to judge you by, so they treat your first sends with suspicion. Send a burst of cold outreach into that vacuum and the providers read it as exactly what spammers do: a cold domain pushing volume with no track record.
Warmup builds that missing history on purpose. You send small amounts of mail that gets opened, replied to, and marked as important, which teaches the inbox providers that real people want your messages. Skip this and you are not just risking one campaign. You can burn the domain permanently, which is why serious senders never run cold traffic on a domain they also use for company email.
What a gradual ramp actually looks like
The pattern is simple: start low, increase a little each day, and watch how the mailbox responds. There is no single magic schedule, but a realistic ramp for a new mailbox looks roughly like this.
- Days 1 to 7: a handful of warmup emails per mailbox per day, climbing slowly.
- Days 8 to 14: tens of emails per day as engagement holds steady.
- Days 15 to 28: approaching your steady-state cap, with cold sends layered in carefully near the end.
The exact numbers matter less than the principle. You are looking for smooth, steady growth with healthy replies, not a spike. If complaints or bounces climb, you slow down rather than push through.
Daily send caps per mailbox
Once a domain is warmed, the instinct is to crank volume. Resist it. A single mailbox should carry a modest daily cap, often somewhere between 30 and 50 cold sends per day, because piling more onto one address looks unnatural and erodes reputation fast. This is the real reason serious outbound runs across many mailboxes and several sending domains instead of one.
That structure is also why owning your sending infrastructure matters. When you control the domains and mailboxes, you can spread volume sensibly, retire an address that gets flagged, and warm new ones in the background. If you want the deeper version of this, our notes on deliverability walk through how the whole system fits together.
Automating warmup so it actually happens
The reason warmup gets skipped is that it is tedious. Nobody wants to hand-send small batches of email for three weeks. So we automate it. Warmup tooling sends and replies to messages across a network of real mailboxes on a schedule, ramps the volume for you, and keeps engagement looking human, all without anyone babysitting it.
In our own stack, warmup runs continuously in the background through Email Bison and our self-hosted n8n automations, so a domain is quietly building reputation well before the first prospect ever sees a message. The point is not the specific tools. It is that warmup should be a system that runs on its own, not a chore you hope someone remembers.
Questions, answered.
Can I speed up warmup if I am in a hurry?
Should I warm up the same domain my company uses for normal email?
Do I keep warming a domain after it goes live?
Want this built and run for you?
LongRun builds the outbound system, runs it, and hands it over at day 90. Book a strategy call to scope yours.