Why warmup emails appear in your Sent folder

WS
WarmySender Team
Updated Jul 27, 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, one filter on the text [ref: in the subject line clears them out of sight in about 30 seconds — the exact clicks for Gmail and Outlook are below.

WarmySender is a 4-pillar outreach platform — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel sequences. 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 — with a single rule. Match on the literal text [ref: in the Subject; you do not need the closing bracket or the code itself.

In Gmail

  1. Open Settings → See all settings → Filters and Blocked Addresses → Create a new filter.
  2. In the Subject field, type [ref:
  3. Click Create filter, then tick Apply the label and choose or create a label such as "Warmup". Ticking Skip the Inbox (Archive it) as well keeps them out of your inbox too.
  4. 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 when you want to see only the mail you wrote.

In Outlook

  1. Open Settings → Mail → Rules → Add new rule.
  2. Name the rule something like "Warmup".
  3. Set the condition to Subject includes and enter [ref:
  4. Set the action to Move to and pick a folder — create one called "Warmup" if you do not have a suitable folder yet.
  5. Save the rule. In the Outlook desktop app you can also select the existing messages in Sent Items and run the rule once to clear the backlog.

Outlook rules apply to new mail from the moment you save them, so the backlog already in Sent Items stays put until you move it. Sorting Sent Items by subject makes it quick to select the tagged messages in one block and drag them across.

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. A rule matching [ref: covers both sides at once if you would rather not see any warmup mail anywhere.

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?

Create one rule that matches the text [ref: in the subject line. Every warmup subject ends with a short tag like [ref: AB12CD34], so that single rule catches all of them. In Gmail: Settings → Filters and Blocked Addresses → Create a new filter, put [ref: in the Subject field, and apply a label such as "Warmup". In Outlook: Settings → Mail → Rules → Add new rule, condition "Subject includes" [ref:, action "Move to" a folder you choose.

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

Rules in Outlook apply to new 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 see no warmup mail anywhere, one rule matching [ref: covers both.

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.