Inbox warmup

Before a new email inbox can reliably send cold emails, it needs to build a reputation — a trust record with Gmail, Outlook, and other email providers that says "this inbox belongs to a real person sending normal email." The process that builds that reputation is called warmupwarmup, and it runs automatically on every inbox you have.

This page covers what warmup does, what to look for on your inbox to know it's ready, and what to do if the numbers don't look right.

Why warmup matters

Email providers punish brand-new inboxes. If a freshly-created inbox sends 500 emails on day one, Gmail treats it as a spammer and starts dropping emails straight into spam folders. Once that happens, it's hard to recover — and it hurts every campaign you run from that inbox afterwards.

Warmup fixes this by sending small, normal-looking emails between inboxes in our network every day. Those emails get opened, replied to, and marked as "not spam" — the same signals a real person's email account generates. Over time, Gmail and Outlook see a record of normal behaviour and start trusting the inbox. Then your real campaigns can go out and land where you want them to.

Think of it like breaking in a new pair of shoes. You don't run a marathon on day one. You wear them around the house, then on short walks, then on longer ones. By the time you run the marathon, they fit. Warmup is the same idea, but for your sending reputation.

Two kinds of warmup

There are two kinds of warmup. Which one your inbox is on tells you whether it's ready to run campaigns.

Inboxes you buy as pre-warmed skip the initial phase. They arrive already through 4+ weeks of warmup, so the flame icon is green on day one and they're ready to send.

Inboxes that are done-for-you (DFY) start with the orange flame and need the 2-week initial warmup window. Do not attach them to campaigns while the flame is orange. Gmail will punish them hard if they send real cold emails before they've built a reputation, and you'll have to rotate them out within weeks.

The health score

Alongside the flame icon, each inbox has a health scorehealth score — a percentage between 0% and 100%.

The score is built from what happened to the last batch of warmup emails your inbox sent. If most of them landed in other inboxes' actual inbox (not spam), the score is high. If some landed in spam, the score drops.

What the numbers mean

• 90% or higher — The inbox is in good shape. Safe to use for campaigns.
• Between 80% and 90% — Treat it as a warning sign. Keep warmup running, avoid pushing new campaign volume through it, and watch campaign reply rate including auto-replies.
• Below 80% — Something's seriously wrong. Pause the inbox from campaigns while you investigate; replacing the inbox is usually safer than trying to force recovery.
• A dash (—) — Not enough data yet. The inbox is brand new; give it a few more days.

What the health score does NOT tell you

The health score only reflects what's happening to warmup traffic. It doesn't directly measure whether your real campaign emails are reaching real prospects. Think of it as a general reputation indicator — a necessary-but-not-sufficient signal. An inbox can have a 95% health score and still struggle on campaigns if your list is bad, your copy is spammy, or you're sending too much volume too fast.

You'll know it's ready when…

Your inbox is campaign-ready when all of these are true at the same time:

1. The Status column shows Active (green) — not Paused, Error, or Warmup.
2. The flame icon is green — not orange.
3. The Health Score is 90% or higher — or just a dash if the inbox is brand-new but the flame is already green.

If all three are true, you can add the inbox to a campaign. If any one of them is off, wait — or fix that one thing first.

If something's not right

The health score dropped a lot this week

Usually one of three things caused it:

• A recent campaign had a high bounce rate. Every bounce hurts reputation. Check the Bounced leadsBounced leads on your last-sent-from campaign — if more than 5% bounced, the list was the likely cause, not the inbox.
• Campaign volume ramped too aggressively for the inbox's reputation. The platform never sends more than 35 campaign emails per inbox per day, but a weak inbox can still struggle if it was used before it was ready or if multiple campaigns put pressure on it as soon as it turned green.
• Your copy tripped spam filters. Phrases like "limited time offer!" or "URGENT" or all-caps subjects can flag the email as spam regardless of the inbox's reputation.

What to do: pause the inbox from all campaigns. Leave warmup running. Check the score again in 5–7 days. Reputation usually recovers on its own if you stop stressing it.

The flame icon is still orange after 2 weeks

Check the inbox's status in the Email Accounts table:

• If status is Error — there's a connection or authentication problem. Click the row and use the Reconnect button. See Health & troubleshooting.
• If status is Paused — you paused the inbox or its warmup. Re-enable it.
• If status is Warmup — there may have been volume hiccups during the initial 2 weeks. Give it another 3–5 days.
• If it's been more than 3 weeks and still orange — contact support with your inbox email address. We can investigate the warmup logs.

My inbox shows 0 warmup emails and no health score

This usually means warmup hasn't started yet. The most common causes:

1. The inbox is still provisioning — pre-warmed domains can take a few hours to fully appear and start warmup activity. Wait 24 hours.
2. The inbox is paused — check the Status column. If it says Paused, re-enable it.
3. The inbox has a connection issue — if the Status column says Error, click the row and use Reconnect. If the row looks healthy but warmup still never starts, contact support with the inbox address.

My inbox's health score is high but my campaigns still aren't getting replies

Warmup health and campaign performance aren't the same thing. If warmup looks good but campaigns don't:

• Check your bounce ratebounce rate on Analytics. Over 5% is the usual culprit — it almost always means list quality, not inbox quality.
• Check your copy. Generic emails to a list that hasn't heard of you rarely get replies, regardless of deliverability.
• Check your angle. Email methods matter more than you'd think.
• Read the deliverability checklist for a full rundown.

Related

• Email Accounts overview — where the flame icon and health score live in the UI
• Health & troubleshooting — fixing broken inboxes
• DFY warmup & reconnect errors — the first two weeks of a DFY inbox and stuck reconnects
• Deliverability — the broader picture
• Buying pre-warmed inboxes — if you need inboxes ready to send immediately