Email warmup explained: how it works and how long it takes

If you connect a fresh mailbox and immediately send a few hundred cold emails, a lot of them will land in spam, and you can damage the sending reputation of that mailbox for weeks. Warmup is how you avoid that. Here is what it is and how to do it sensibly.

What warmup actually is

Mailbox providers like Gmail and Microsoft 365 decide where your email lands partly based on your sending history: do you send consistent, modest volumes that get opened and replied to, or did you appear from nowhere and blast a list? Warmup builds that positive history gradually. It starts with a small daily volume and increases it over time, so by the time you are sending real campaigns, the provider trusts the mailbox.

How long it takes

There is no single number, but a useful rule of thumb is two to four weeks for a brand-new domain or mailbox before you push real volume, ramping a little each day rather than jumping. Older, established mailboxes that already send normal business email need less. The newer the domain, the slower you should go.

Ramp safely

• Start low. A new domain might begin at a handful of sends a day, not fifty.
• Increase gradually, not in one leap.
• Keep your list clean so you are not bouncing, which hurts reputation fast.
• Spread volume across multiple mailboxes rather than overloading one.

Warmup is patience converted into deliverability. The teams who rush it are the ones wondering why their open rates collapsed in week two.

HuntSales runs configurable warmup on your connected mailbox: you set the starting floor and the daily increment, and it ramps for you while monitoring per-mailbox limits. Connect the mailbox, set a conservative floor, and let it build the history before your first big campaign.