Why warmup emails sometimes appear in your inbox

Email warmup works by having real inboxes exchange friendly, natural-looking emails and mark them as wanted — that steady, positive activity is what builds your sender reputation over time. Because warmup runs through your real inbox, a few of these warmup emails briefly land where you can see them. That's completely normal, and you don't need to do anything: WarmySender automatically tidies warmup emails out of your inbox — typically within about a day — so they never pile up. This page explains why you occasionally see them, why a cluster can appear and then disappear when your sending volume changes, and how to filter them yourself if you'd like.

WarmySender is a 4-pillar outreach platform — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel sequences. This guide covers an Email Warmup question: why warmup emails sometimes show up in your inbox.

What warmup actually is

Warmup is a network of real inboxes sending each other genuine, friendly emails — and then opening them, replying to some, and marking them as wanted rather than spam. To a mailbox provider, that pattern looks exactly like a healthy, trusted sender: people are happy to receive your mail and engage with it. Over time, that signal is what lifts your sending reputation so your real campaign emails are more likely to reach the inbox.

The key thing to understand is that warmup uses your actual inbox, not a hidden test account. That's what makes it effective — and it's also why, every now and then, one of these warmup emails is visible to you for a little while.

Why you sometimes see them

Because warmup happens inside your real inbox, some warmup emails briefly arrive where you can see them before WarmySender tidies them away. There's nothing wrong when this happens — it's simply the warmup conversation passing through your inbox the way any real email would.

You'll never be left to clean these up by hand. WarmySender quietly moves warmup emails out of your inbox for you, so they don't clutter your day-to-day view. In most cases this happens within about a day of the email arriving, which is why you might notice one for a short while and then find it gone the next time you look.

WarmySender tidies them for you — automatically

You do not need to delete, archive, or sort warmup emails yourself. WarmySender automatically tidies them out of your inbox so your inbox stays focused on the messages that actually need your attention.

• It's automatic. There's no setting to switch on — tidying warmup mail out of your inbox is part of how warmup runs.
• It's quick. Warmup emails are typically tidied away within about a day of arriving, so they don't accumulate.
• It's safe. Only the friendly warmup emails are tidied — your real mail from real people and your campaign replies are never touched.

So if you spot a warmup email in your inbox, you can safely leave it where it is. It will be tidied away on its own.

Why it can look bursty or inconsistent

One of the most common questions is: "A bunch of these appeared all at once, and now they're gone — is something broken?" The answer is no. The amount of warmup mail you might briefly see tracks your own sending volume.

Here's why. When you send more — for example, you ramp up a campaign or warmup steps up to a higher daily volume — more warmup replies come back at once. Since warmup runs through your real inbox, a few more of them may briefly be visible before they're tidied away, so you can see a short-lived cluster. When your volume is low, the opposite happens: there's much less warmup activity, so you'll rarely see any warmup emails at all.

A quick example

Imagine that for a couple of weeks you were sending a small, steady amount of mail. During that time you barely noticed any warmup emails in your inbox — maybe one here and there. Then you launch a bigger campaign and warmup volume rises to keep pace. Over the next day or two you glance at your inbox and notice a handful of warmup emails sitting there at once. A day later they're gone, and as your sending settles into its new rhythm you stop noticing them again.

That whole sequence — quiet, then a brief cluster, then tidied away — is exactly what's expected. It tracks your volume, not a glitch. More sending means more warmup activity passing through your inbox; the automatic tidy-up keeps it from ever building up.

Filter or auto-archive them yourself (optional)

WarmySender already tidies warmup emails for you, so this step is entirely optional. But if you'd prefer to keep them out of sight the moment they arrive — or route them to their own label or folder — you can set up a simple filter in your email app.

Every warmup email's subject line ends with a short tag that looks like this:

• [ref: AB12CD34]

The letters and numbers change from email to email, but the [ref: part is always there. That makes it easy to match every warmup email with one rule.

In Gmail

1. Open Settings → Filters and Blocked Addresses → Create a new filter.
2. In the Subject field, type [ref:
3. Click Create filter, then choose what you'd like to happen — for example, Skip the Inbox (Archive it) and/or Apply a label like "Warmup".

In Outlook

1. Open Settings → Mail → Rules → Add new rule.
2. Set the condition to Subject includes [ref:
3. Set the action to Move to a folder of your choice (for example, a "Warmup" folder), then save.

With a rule like that in place, any email whose subject contains [ref: is filed away automatically — a tidy belt-and-braces option on top of the cleanup WarmySender already does for you.

Frequently asked questions

Why do warmup emails show up in my inbox?

Because warmup works by using your real inbox, not a hidden test account. Real inboxes exchange friendly emails and mark them as wanted, and that genuine activity is what builds your sender reputation. Since it happens in your actual inbox, a few warmup emails briefly land where you can see them. There's nothing wrong when this happens — WarmySender automatically tidies them out of your inbox, typically within about a day, so they never pile up.

Do I need to delete them myself?

No. You don't need to delete, archive, or sort warmup emails — WarmySender tidies them out of your inbox for you automatically. If you spot one, you can safely leave it where it is and it will be cleaned up on its own, usually within about a day. There's no setting to turn on; it's simply part of how warmup runs.

How long until they disappear?

Warmup emails are typically tidied out of your inbox within about a day of arriving. That's why you might notice one for a short while and then find it gone the next time you check. You don't have to wait by the inbox or do anything — the cleanup happens in the background.

A bunch appeared at once and then disappeared — is something broken?

No, that's completely normal. The amount of warmup mail you might briefly see tracks your own sending volume. When you send more — say you ramp up a campaign — more warmup replies come back at once, so you can see a short-lived cluster before they're tidied away. When your volume is low, you'll rarely see any. So "quiet, then a brief cluster, then gone" is expected behavior; it follows your volume, not a glitch.

What if I see too many at once?

Seeing several at once usually just means your sending volume recently went up, which is a healthy sign that warmup is keeping pace. They'll be tidied away automatically, typically within about a day. If you'd rather not see them at all in the meantime, you can set up a simple filter in Gmail or Outlook that matches the subject text [ref: and archives or files those emails for you.

How can I filter warmup emails myself?

Every warmup email's subject line ends with a short tag like [ref: AB12CD34]. The letters and numbers change each time, but the [ref: part is always there. Create a filter in Gmail (Settings → Filters → Create a new filter) or a rule in Outlook (Settings → Mail → Rules) where the subject includes [ref:, then choose to archive it or move it to a folder. This is optional — WarmySender already tidies warmup emails for you — but it's there if you'd like an extra layer of organization.

Will tidying warmup emails touch my real mail?

No. Only the friendly warmup emails are tidied out of your inbox. Your real messages from real people and your campaign replies are never moved or hidden. Warmup is designed to work quietly in the background and leave the mail that actually matters to you exactly where it belongs.

Still seeing a lot of warmup emails?

If warmup emails are noticeably building up in your inbox and not being tidied away, we'd like to take a look. Email [email protected] with the mailbox address and a screenshot, and we'll check it for you.

Related reading

• Understanding your warmup Inbox Rate — what the number means and why it's accurate
• How email warmup ramps up — what to expect in your first hour, first day, and first week
• Email Warmup FAQ — how warmup builds and protects mailbox reputation across the network of senders
• Your mailboxes — check warmup status and activity per mailbox
• Full documentation — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel guides