Why warmup emails appear in your Sent folder

WS
WarmySender Team
Updated Aug 13, 2026

If your Sent folder is full of warmup messages, here is the short answer: your email provider put them there, not WarmySender. Warmup is sent from your real mailbox, and providers like Outlook and Microsoft 365, Gmail, Yahoo, AOL and iCloud automatically keep a copy of everything sent from your account in Sent — every message, whoever or whatever sent it. WarmySender never saves a warmup message to your Sent folder. Nothing is broken, and seeing them there actually confirms warmup is running. If they are getting in your way, a filter matching [ref: in the subject and your own address in the From line clears them out of sight in about 30 seconds — the exact clicks for Gmail and Outlook are below. That second condition matters: it keeps the rule on the copies you sent, and leaves the warmup arriving from other people alone.

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 answers an Email Warmup question: why warmup messages appear in the Sent folder, and how to hide them.

Why they are there

Email warmup works by having real mailboxes exchange friendly, natural-looking messages and mark them as wanted. That steady, positive activity is what builds your sending reputation over time — and it only works because it runs through your real mailbox, not a hidden test account.

Most email providers keep their own record of everything that leaves your mailbox. The moment a message is sent from your address, the provider files a copy into your Sent folder itself, before anything else happens. It does this for mail you typed by hand, for mail sent from your phone, for mail sent by any app connected to your account — and for warmup. From the provider's point of view there is no difference: it is all mail sent from you.

So on those providers, warmup shows up in Sent as a matter of course. It is your provider's normal behavior, applied to your mailbox, exactly as it would be for anything else you send.

Which providers do this

These providers keep their own copy of outgoing mail in Sent, so warmup will appear there:

Mailboxes on a custom domain with a smaller host often do not save outgoing mail automatically. On those, warmup usually will not appear in Sent at all — which is why two people on the same plan can genuinely have different experiences here. It comes down to who hosts the mailbox.

WarmySender does not put them there

This is worth stating plainly, because it is the part customers most often assume: we never save a warmup message into your Sent folder. Warmup is automated background activity, not mail you wrote, so filing a copy under "sent by you" would be misleading and would eat into your mailbox storage for no benefit. We deliberately do not do it.

Your real outgoing mail is treated differently, and on purpose. Campaign emails, sequence steps and replies you send from WarmySender are saved to Sent on providers that do not do it themselves, so the mail you actually composed sits alongside everything else you have sent. On Outlook and Gmail we skip that step, because those providers already save it — doing it as well would give you two copies of every message.

Put together: if you are on Outlook, Gmail, Yahoo, AOL or iCloud, every warmup message in your Sent folder is a copy your provider made. There is no second copy from us.

Hide them with one filter (about 30 seconds)

You cannot stop your provider from saving its own copy — that setting belongs to them, not to us. What you can do is tell your mailbox to move those copies out of the way automatically, so Sent goes back to showing the mail you actually wrote.

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

The letters and numbers change from message to message, but the [ref: part is always there. That makes it easy to match every warmup message — past and future. Match on the literal text [ref: in the Subject; you do not need the closing bracket or the code itself.

Then add one more condition: your own email address in the From line. That second condition is what keeps the rule pointed at the copies you sent. On its own, a subject-only rule also matches the warmup arriving from other people — so it would quietly file your incoming warmup away too, which is not what you came here to do. Both recipes below include it.

In Gmail

  1. Open Settings → See all settings → Filters and Blocked Addresses → Create a new filter.
  2. In the From field, type your own email address — the address of the mailbox you are warming up. This is the step that keeps the filter to your sent copies.
  3. In the Subject field, type [ref:
  4. Click Create filter, then tick Apply the label and choose or create a label such as "Warmup sent".
  5. Leave Skip the Inbox (Archive it) unticked. It does nothing useful for sent copies, and it is the tick that would hide warmup arriving from other people.
  6. Tick Also apply filter to matching conversations before you save, and the messages already sitting there are labelled straight away.

Gmail shows Sent as a label rather than a folder, so the tidiest result is to label warmup mail and then simply search or browse in:sent -label:"Warmup sent" when you want to see only the mail you wrote.

In Outlook

Outlook's Settings → Mail → Rules screen only runs on mail arriving in your inbox, so it cannot tidy Sent Items — a rule made there would catch incoming warmup instead. Do this rather than that:

  1. Create a folder called "Warmup sent" (right-click your mailbox name → Create new subfolder).
  2. Open Sent Items and click the search box above the message list.
  3. Set the search scope to Current folder, type [ref: and press Enter.
  4. Select everything it finds (Ctrl+A, or Cmd+A on a Mac) and drag it into your "Warmup sent" folder.
  5. To make it automatic, use the Outlook desktop app: File → Manage Rules & Alerts → New Rule → Apply rule on messages I send, condition with specific words in the subject → [ref:, action move it to the specified folder → "Warmup sent". Starting from messages I send is what keeps it off your incoming mail.

Anything already sitting in Sent Items stays put until you move it — the search above is the quickest way to grab the whole backlog in one go.

What if I also want a rule for the warmup that arrives?

That is fine, and it will not cost you anything: we look for warmup wherever your mailbox has filed it, not only in the inbox, so a label or folder of your own still counts. Worth knowing, though: leaving incoming warmup in the inbox is the closest match to how ordinary mail behaves, and behaving like ordinary mail is exactly what warmup is teaching your provider to expect. If you have no strong preference, leave the arriving side alone — the recipes above deliberately touch only the copies you sent.

Finding your real replies again

If what you actually wanted was to find genuine campaign replies rather than tidy up Sent, you can also read and answer them inside WarmySender — replies to your campaigns are collected in your unified inbox, so you are not digging through a mailbox to find them.

Your inbox is already handled for you

Warmup messages that arrive in your inbox are a different story: those are tidied out of your inbox automatically, typically within about a day, so they never build up. You do not have to do anything about those, and you do not need a filter for them.

That is why this page is really about the Sent folder. The copy your provider makes when a message goes out belongs to your provider, so it stays where your provider put it until you tell your mailbox otherwise. That is also why the recipes above match on your own address as well as on [ref: — a subject-only rule would reach across to the arriving side too, and the arriving side already looks after itself.

More on the inbox side: Why warmup emails sometimes appear in your inbox.

Does this hurt my deliverability?

No. A copy sitting in your Sent folder is simply a record on your own mailbox — it has no bearing on whether your mail reaches anyone's inbox, and mailbox providers do not judge your reputation on what your Sent folder contains. Filtering, moving or deleting those copies does not affect warmup either: warmup keeps running exactly as before, and your warmup results are unchanged.

The one practical thing worth watching is storage. Sent copies do take up room in your mailbox, and a mailbox that runs out of space can start rejecting incoming mail. If your mailbox is close to full, moving warmup copies out of Sent will not free anything on its own — you would need to delete them, or empty the folder they were moved to, to actually reclaim the space.

Frequently asked questions

Why are warmup emails in my Sent folder?

Because your email provider keeps its own copy of everything sent from your mailbox. Warmup goes out from your real mailbox, so your provider files a copy in Sent exactly as it does for mail you write yourself. Outlook and Microsoft 365, Gmail, Yahoo, AOL and iCloud all behave this way. WarmySender never saves warmup messages to your Sent folder — the copy you are looking at was made by your provider.

Can WarmySender stop them from being saved?

No, and neither can any other tool. Saving a copy of outgoing mail is something your provider does on its own side, at the moment the message is sent. It is their behavior, applied to your whole mailbox. The practical fix is a filter or rule in your mailbox that moves warmup copies out of Sent automatically — it takes about 30 seconds to set up and works from then on.

How do I stop warmup emails cluttering my Sent folder?

Match two things, not one: the text [ref: in the subject AND your own address in the From line. Every warmup subject ends with a short tag like [ref: AB12CD34], and adding your own address is what keeps the rule to the copies you sent instead of also catching the warmup arriving from other people. In Gmail: Settings → See all settings → Filters and Blocked Addresses → Create a new filter, put your own address in the From field, put [ref: in the Subject field, then apply a label such as "Warmup sent". Leave "Skip the Inbox" unticked. In Outlook, the Rules screen only runs on mail arriving in your inbox, so it cannot tidy Sent Items: open Sent Items, search it for [ref:, select the results and move them to a folder you have made. In the Outlook desktop app you can automate it with a rule that starts from "Apply rule on messages I send".

I set up the rule but the old ones are still in Sent Items — why?

Rules apply to mail from the moment you save them, so anything already in Sent Items stays where it is. Sort Sent Items by subject, select the block of tagged messages, and move them to your Warmup folder in one go. In Gmail, tick "Also apply filter to matching conversations" while creating the filter and the existing ones are handled for you.

Will filtering or deleting them break warmup?

No. Those copies are just a record on your own mailbox. Moving them, labelling them or deleting them does not affect warmup, does not affect your warmup results, and does not affect your sending reputation. Warmup carries on exactly as before.

My colleague on the same plan doesn't see this — why?

Because it depends on who hosts the mailbox, not on your plan. Outlook, Microsoft 365, Gmail, Yahoo, AOL and iCloud save outgoing mail automatically. Many custom-domain hosts do not, so on those mailboxes warmup never shows up in Sent at all. Two people on identical plans can genuinely see different things here.

What about the warmup emails in my inbox?

Those are tidied out of your inbox automatically, typically within about a day, so they never pile up and you do not need to do anything. The Sent folder is the side that needs a filter, because the copy there was made by your provider. If you would rather file the incoming ones into their own label or folder as well, that is fine — warmup still counts them, because we look for warmup wherever your mailbox has filed it, not only in the inbox. Leaving them in the inbox is simply the closest match to how ordinary mail behaves, which is what warmup is teaching your provider to expect, so it is the better default if you have no strong preference either way.

Do these copies use up my mailbox storage?

Yes, in the same way any other message in your mailbox does. If your mailbox is close to full, moving warmup copies to another folder will not free space on its own — you would need to delete them, or empty the folder you moved them into, to reclaim it. A mailbox that runs out of room can start rejecting incoming mail, so it is worth keeping an eye on if you are near your limit.

Still stuck?

If warmup messages are still getting in your way after setting up a filter, or something does not look right, email [email protected] with the mailbox address and a screenshot, and we will take a look for you.

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