Why warmup emails sometimes appear in your inbox

WS
WarmySender Team
Updated Sep 9, 2026

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 — it waits at least a day, and clears them within two — so they never build up. Because of that deliberate wait, the most recent day or two of warmup mail is always sitting in your inbox by design: if your mailbox is set to 40 warmup emails a day, expect to see roughly 40 to 80 of them there at any time. This page explains why the wait exists, how to tell the cleanup is doing its job, and how to hide warmup mail from view in about thirty seconds if you'd rather not see it at all.

WarmySender runs your outreach on autopilot with AI agents, across Cold Email, Email Warmup, LinkedIn, Instagram and Multichannel sequences — plus real-time email verification. 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. The cleanup deliberately waits at least a day after an email arrives, and clears it within two — so a warmup email you notice this morning is meant to still be there tonight, and gone in a day or so. What you're looking at is a rolling window of the last day or two, not a backlog.

Does WarmySender automatically archive warmup emails?

Yes. Warmup emails that arrive in your inbox are cleared out for you automatically — at least a day after they land, and within two. You do not need to delete, archive, sort, or filter anything yourself, and there is nothing to switch on — it is simply part of how warmup runs, on every mailbox with warmup enabled, on every plan.

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

How many should I expect to see at any time?

This is the part that surprises people. Because the cleanup deliberately waits a day and can take up to two, your inbox always holds the most recent day or two of warmup mail. That is not a cleanup that failed to run — it is the design.

The rough maths is simple: take your mailbox's daily warmup volume and expect between one and two days' worth to be visible.

That steady, unremarkable stack of recent mail is a large part of what makes your mailbox look natural to providers: a healthy inbox receives mail every day and keeps it for a while. An inbox that empties itself the instant anything arrives does not look like anyone's real mailbox.

How can I tell the cleanup is working?

Look at the age of the warmup mail, not the amount. Search your inbox for [ref: and sort by date:

A full-looking but recent stack, with nothing older sitting behind it, is exactly the shape you should see.

Are they moved, or actually deleted?

It depends on who provides the mailbox, and the difference is worth knowing if you are ever short on storage.

Why does it wait a day or two?

The delay is deliberate, not a backlog. A warmup email only helps your reputation once it has finished doing its job: arriving, being opened, being replied to, and being rescued from spam if it landed there — and then being counted toward the placement figures of the mailbox that sent it, not your own. All of that takes time to play out naturally, the same way a real conversation would. If we removed the message the moment it arrived, we would be throwing away the very signal it was sent to create — and your warmup statistics would be measuring mail that was no longer there.

So each message is left alone for at least a day until it has finished counting, and cleared within two. It also means a warmup email you notice this morning is supposed to still be sitting there this evening — that is the system working correctly, not a missed cleanup.

The one exception: your Sent folder

Automatic cleanup covers your inbox and your spam folder. It does not cover your Sent folder, and that is intentional. We never file warmup into Sent ourselves — but Gmail, Outlook and Microsoft 365, Yahoo, AOL and iCloud all keep their own copy of everything sent from your mailbox, saved on their side the moment the message goes out. We deliberately never delete from Sent, because that folder also holds your genuine campaign sends and the mail you wrote by hand, and a mistake there would be unrecoverable. If those copies bother you, the [ref: filter below hides them in about thirty seconds, and Why warmup emails appear in your Sent folder has the click-by-click recipe.

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:

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, waiting at least a day and clearing them within two, so the most recent day or two is visible and nothing older builds up.

Does WarmySender automatically archive warmup emails?

Yes. Warmup emails that arrive in your inbox are cleared out automatically — at least a day after they land, and within two — and your spam folder is covered on the same schedule. There is nothing to switch on and nothing to configure — it applies to every mailbox with warmup running, on every plan. On Gmail and Google Workspace the messages are moved to All Mail, the same as Gmail's own Archive, so you can always find them again by searching. On every other provider they are deleted permanently, which frees the storage back up. Your Sent folder is the one place this does not reach, because your provider keeps its own copy there and that folder also holds your real mail.

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 within a day or two. There's no setting to turn on; it's simply part of how warmup runs.

How long until they disappear?

Each warmup email is left alone for at least a day after it arrives, and cleared within two. That wait is deliberate, so the most recent day or two of warmup mail is always visible in your inbox — if your mailbox is set to 40 warmup emails a day, expect to see roughly 40 to 80 of them there at any time. Nothing older than that should be building up behind them.

How many warmup emails should I expect to see in my inbox?

Between one and two days' worth, because the cleanup waits at least a day and can take up to two. At 40 warmup emails a day that's roughly 40 to 80 visible at any moment; at 20 a day, roughly 20 to 40. That is normal and intentional — a mailbox that receives mail and keeps it for a while is exactly what looks natural to providers. To check the cleanup is working, look at the age rather than the number: warmup mail from three or more days ago should not be sitting in your inbox.

Why does it wait a day or two rather than happening immediately?

Because each warmup email has to finish counting toward your warmup first. A message only helps your reputation once it has arrived, been opened, been replied to, been rescued from spam if it landed there, and been counted toward the placement figures of the mailbox that sent it, not your own — and that takes time to play out naturally, just as a real conversation would. Removing it sooner would throw away the very signal it was sent to create, and your warmup statistics would be measuring mail that was no longer there. So each message is left alone for at least a day until it has done its job, then cleared within two. That is also why the most recent day or two of warmup mail is always visible — it is still doing its work.

Are the warmup emails moved or permanently deleted?

It depends on your provider. On Gmail and Google Workspace they are moved to All Mail — exactly what Gmail's own Archive button does — so nothing is destroyed and you can find them again by searching. Because they still exist in the account, they still take up storage, though Gmail accounts have far more room so this rarely matters. On every other provider they are removed for good rather than filed elsewhere, which genuinely frees the space back up. Either way, only warmup mail is in scope: your real messages and campaign replies are never touched.

Does the cleanup cover my spam folder too?

Yes. Warmup mail is sometimes filtered into spam before it gets rescued, so the spam folder is cleared on the same schedule as your inbox. That stops rescued warmup mail from quietly collecting there. Only warmup emails are affected — anything else in your spam folder is left exactly as it is.

Does it clean up my Sent folder as well?

No, and that is deliberate. WarmySender never files warmup into your Sent folder itself, but Gmail, Outlook and Microsoft 365, Yahoo, AOL and iCloud all keep their own copy of everything sent from your mailbox, saved on their side the moment it goes out. We never delete from Sent because that folder also holds your genuine campaign sends and the mail you wrote by hand, and getting that wrong would be unrecoverable. To hide those copies, use the same [ref: subject filter described above, or see Why warmup emails appear in your Sent folder for the step-by-step.

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 a stack of them is expected: the cleanup waits at least a day and clears within two, so one to two days' worth is always there — 40 to 80 of them on a mailbox set to 40 a day. A larger cluster than usual normally just means your sending volume recently went up, which is a healthy sign that warmup is keeping pace. If you'd rather not see them at all, set up a simple filter in Gmail or Outlook that matches the subject text [ref: and archives or files those emails for you — that hides them instantly, and warmup still counts them wherever your mailbox files them.

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?

One to two days' worth of warmup mail is expected. But if you're finding warmup emails from three or more days ago still sitting in your inbox, that's a genuine build-up and we'd like to take a look. Email [email protected] with the mailbox address and a screenshot, and we'll check it for you.

Still have questions? Email [email protected] — we respond within 24 hours on business days.