# Why is warm-up not running?

> A mailbox is not warming up: the connection step almost everyone misses, where to check it, and what warm-up does and does not do for a brand-new domain.

**Enabling warm-up on a mailbox and connecting it to the warm-up service are two separate steps, and the second is the one people miss. Open the mailbox's own warm-up tab and confirm it shows as connected, not just switched on.**

_Status: Reviewed – written against Reply's product documentation on 2026-09-21, not yet confirmed against the running product._

## Quick fix

1. Open **Settings → Email Accounts**, select the mailbox, and open its **Warm-up** tab. This is the reliable route; the warm-up section elsewhere in the menu is not always where people expect.
2. Check whether the mailbox is **connected**, not just whether the toggle is on.
3. If it is not connected, use **Connect** and save, then wait for the mailbox to appear as active.
4. Confirm the mailbox itself is connected and healthy; warm-up cannot run through a mailbox that cannot send.
5. Check again the next day. Warm-up activity is low by design at the start and is easily missed.

Didn't work? [Contact Reply support](https://support.reply.io/); the team can check your account directly.

## Symptom

Warm-up appears enabled but no warm-up mail is being sent or received, or a mailbox added recently never started warming while others did.

## Most likely causes

| Cause | How to recognize it |
| --- | --- |
| **The mailbox was never connected to the warm-up service** | The toggle is on and the mailbox's warm-up tab does not show it as connected. By far the most common |
| The mailbox itself is disconnected | Warm-up depends on the mailbox being able to send and receive – see [Why was a mailbox disconnected?](/troubleshooting/mailbox-was-disconnected/) |
| Warm-up seats are used up | A new mailbox cannot be added to warm-up while the allowance is full |
| It is running, quietly | Early warm-up volume is deliberately small. Nothing visible does not mean nothing happening |
| The domain is failing authentication | Warm-up mail from an unauthenticated domain bounces – see [Why does my domain fail its DNS check?](/troubleshooting/domain-fails-dns-check/) |
| The mailbox was suspended | The provider restricted it, so nothing sends, warm-up included |

## Diagnostic checklist

1. **Check connected, not enabled.** These are different states and the difference is the answer most of the time.
2. **Check the mailbox's own health first.** Warm-up rides on the mailbox; a disconnected mailbox warms nothing.
3. **Check the seat allowance** if the mailbox is new and others are warming normally.
4. **Check the domain's authentication.** Warm-up on a domain that fails authentication does harm rather than good.
5. **Give it a day before concluding anything.** Warm-up starts small on purpose.

## Resolution

### It was never connected

Open the mailbox's **Warm-up** tab, use **Connect**, choose a profile and save. Warm-up begins on the next cycle rather than immediately.

### The mailbox is disconnected

Fix the mailbox first. Warm-up resumes on its own once the mailbox can send and receive again.

### Warm-up seats are full

Either free a seat by removing warm-up from a mailbox you no longer send from, or add capacity. A mailbox cannot warm without a seat.

### Authentication is failing

Fix SPF, DKIM and DMARC before warming. Warming an unauthenticated domain teaches receivers the wrong thing about it.

### It is running and you cannot see it

Check again over a few days rather than a few hours. Volume climbs gradually; that gradualness is the entire point.

## Verification

Open the mailbox's warm-up tab and confirm it reports as connected and active. Then check again after two or three days and confirm volume is climbing rather than flat.

## Prevention

- Connect warm-up as part of adding a mailbox, not as a later step. This one habit prevents most of these.
- Authenticate the domain before warming it.
- Keep warm-up running after the initial period rather than switching it off once outreach starts.
- Track your warm-up seat usage so a new mailbox does not silently fail to start.

## FAQ

### How long before I can start sending?

Give a new mailbox a few weeks of warm-up before real volume, and keep warm-up running afterwards. There is no single number; a new domain needs longer than a new mailbox on an established one.

### Can I send while warm-up is running?

Yes, at low volume, and keep warm-up on. Ramp up gradually rather than switching from warm-up straight to full sending.

### Should I turn warm-up off once I am sending?

No. Leaving it running maintains the reputation it built.

## Still stuck? Contact Reply support

If these steps didn't solve the problem, the Reply support team can look at your
account directly. Open the [Reply Help Center](https://support.reply.io/) and send
the team a message.

To get an answer faster, include:

- the mailbox, and whether its warm-up tab reports it as connected
- whether the mailbox itself is connected and sending
- when you added it, and when you expected warm-up to start
- whether the domain passes its authentication check

Don't send passwords, API keys, or access tokens.

## Related

- [Why was a mailbox disconnected?](/troubleshooting/mailbox-was-disconnected/)
- [Why does my domain fail its DNS check?](/troubleshooting/domain-fails-dns-check/)
- [Why are my emails going to spam?](/troubleshooting/emails-going-to-spam/)

## Build with Reply

- REST API: [Email accounts](https://docs.reply.io/api-reference/introduction) – read a mailbox's warm-up state
- MCP: [docs.reply.io/mcp](https://docs.reply.io/mcp/overview) – check warm-up across mailboxes from an assistant