Why did my warmup volume go down?

Because some of that mailbox's warmup emails have been landing in spam instead of the inbox, so WarmySender has deliberately eased its daily warmup volume back while things improve. It only affects warmup on that one mailbox, your campaigns keep sending, nothing is deleted, and the volume lifts again on its own once the mailbox's inbox placement recovers. You will see it as a much smaller number of warmup emails per day than usual — often just a few, sometimes only one.

There are two versions of this, and it is worth knowing which one you are looking at, because one of them needs nothing from you and the other needs a fix:

• We are still building a picture of this mailbox. Only a small amount of warmup mail has been placed so far, one or two pieces went to spam, and that genuinely is not enough to judge a mailbox on. The mailbox gets a small daily allowance so it can build up a real picture — typically a few days to about a week.
• This mailbox really is landing in spam. Enough warmup mail has been placed to be confident about it, and too much of it is being filtered. Volume drops right down to protect the reputation you are building — typically a couple of weeks, and usually there is something underneath worth fixing.

WarmySender is an agentic outreach platform covering Cold Email, Email Warmup, LinkedIn, Instagram and Multichannel sequences, plus real-time email verification. This guide covers an Email Warmup question: why a mailbox's daily warmup volume can be reduced, and how it comes back.

Which of the two am I in?

Look at how much warmup that mailbox has actually placed, and at how small the daily number is. The two states look similar at a glance but behave differently:

If you are not sure which one you are in, the safe answer is the same for both: leave warmup switched on and give it time. Turning warmup off, or removing and re-adding the mailbox, makes both states last longer, because both of them are waiting on the mailbox to build up a fresh run of inbox placements.

Why does WarmySender reduce volume at all?

Because sending more mail from a mailbox that is currently being filtered is the fastest way to make the problem permanent. Warmup works by having real inboxes exchange friendly emails and treat them as wanted, which gradually teaches mail providers that your mail belongs in the inbox. That only works while your mail is actually reaching the inbox.

Once a meaningful share of it starts going to spam instead, every extra email is reinforcing the wrong lesson — you are teaching providers, at volume, that mail from your domain is the kind that gets filtered. So rather than push on, WarmySender eases that one mailbox's daily volume back, lets the placement settle, and picks the pace up again as things improve.

It is the same instinct as easing off rather than forcing it. A quiet week costs you a little time. A domain that has taught every major provider to filter it costs you weeks, and sometimes a new domain.

Where is the line?

Roughly one in twenty — about 5% of a mailbox's warmup emails landing in spam rather than the inbox, measured over the last week. Under that, the mailbox warms at its normal pace and ramps toward the target you set. At or above it, volume is reduced while placement recovers.

Two things worth knowing about that number:

• It is measured on warmup only. Your campaign results — opens, replies, bounces — are tracked separately and never feed into this. One never distorts the other.
• There is a second, higher line further up. If a mailbox goes past roughly 15%, it is also kept out of the pool of mailboxes that other people's warmup gets sent to, so a struggling mailbox is never asked to carry someone else's reputation while it sorts itself out. That higher line is about protecting the network; the 5% one is about protecting you. Volume reduction starts at the lower of the two.

Why isn't a brand-new mailbox judged on its first two emails?

Because a percentage calculated from a handful of emails is not really a percentage — it is a coin toss wearing a percent sign. This is the single most important thing on this page, so here it is with numbers.

Imagine a mailbox that has placed just two warmup emails all week. One reached the inbox, one went to spam. On paper that is a 50% spam rate — which sounds catastrophic. But it is one email. A perfectly healthy mailbox has unremarkable days where a single message gets filtered; that tells you almost nothing about the mailbox.

Now imagine a mailbox that has placed a hundred warmup emails this week, and fifty of them went to spam. That is the same 50% — but this time it is a real, settled answer about a real problem.

So WarmySender waits until it has enough to be sure before treating a number as a verdict. While it is waiting, the mailbox is given a small daily allowance rather than being held at a trickle — enough to build up a genuine run of placements and earn a real answer, one way or the other. That allowance is always capped by the mailbox's normal ramp for its age, so it can never send more than a healthy mailbox of the same age would.

The alternative is worse than it sounds. A mailbox held at one email a day can only place about seven emails a week — which is nowhere near enough to ever prove it is fine. It would sit there indefinitely, unable to gather the evidence that would set it free. Giving it a small allowance is what turns a dead end into a short wait.

Two worked examples

A new mailbox that got unlucky

You connect a new mailbox on Monday and switch warmup on. Being new, it starts gently — a couple of emails a day. By Wednesday it has placed three warmup emails, and one of them landed in spam. On paper that is 33%.

WarmySender does not treat that as a verdict, because three emails cannot support one. Instead the mailbox keeps a small daily allowance so it can build up a proper run of placements. Over the next few days it places a couple of dozen more, almost all of them straight to the inbox, and the picture resolves: this is a healthy mailbox that had one unlucky message. The allowance lifts and the normal ramp resumes, continuing from where it was rather than starting over.

A mailbox that really is being filtered

A mailbox has been warming for six weeks and sending forty warmup emails a day. Its domain's authentication was changed and now a large share of its mail is being filtered — this week, twenty out of eighty warmup emails went to spam. That is 25%, on plenty of evidence, so it is a genuine answer rather than noise.

Volume drops right down while the reputation is protected. You check the domain's authentication, find the problem, and fix it. Over the following couple of weeks the mailbox's placement climbs back, the spam share falls below the line, and volume ramps back up on its own. Nothing needed switching back on.

How long does it last?

Days for the "still building a picture" state, and typically one to three weeks for a mailbox that really is landing in spam. In both cases it lifts by itself — there is no button to press and no support ticket required.

• Still building a picture: usually a few days to about a week. The mailbox just needs to place enough warmup mail for the answer to become clear, and its small daily allowance is sized to get it there.
• Genuinely landing in spam: as long as it takes for the mailbox's placement over the last week to come back under the line. If the underlying cause is fixed, that is usually one to three weeks of steady warmup. If it is not fixed, it can persist — the measurement is honest, so it keeps reflecting what is actually happening.
• Either way, your progress is kept. Reduced volume is not a reset. Your warmup history and the ramp you have built stay exactly where they were, and when volume lifts, it continues from there rather than starting at day one.

Because the measurement covers the last week of activity, changes show up gradually rather than instantly — a good day does not flip it back immediately, and one bad day does not tip it over. That slowness is deliberate: it stops a mailbox flapping between states.

What should I do about it?

Leave warmup running, then work through the causes below in order. The single most common mistake is switching warmup off, or removing and re-adding the mailbox, in the hope of resetting something. That does not reset anything — it just removes the mailbox's only route back, because it needs to keep placing warmup mail to prove it is healthy again.

1. Check your domain's authentication first. SPF, DKIM and DMARC records that are missing, duplicated or wrong are by far the most common reason mail starts being filtered. Fix these before anything else — everything downstream depends on them.
2. Ease off cold sending from that mailbox. Warmup and campaigns share the same reputation. If a mailbox is being filtered, pushing cold volume through it at the same time works directly against the recovery. Pause or slow campaigns on that specific mailbox and let its healthy mailboxes carry the load.
3. Look at the domain's history. A second-hand domain, or one that shares a name with something previously used for bulk mail, can arrive with a reputation already attached. If a domain never recovers despite clean authentication and weeks of steady warmup, that is usually the reason.
4. Check whether it is one mailbox or all of them. If every mailbox on a domain is affected, the cause is at the domain level — authentication, history, or the sending platform behind it. If it is one mailbox out of several on the same domain, the cause is more likely specific to that mailbox.
5. Then leave it alone and let it work. Warmup recovery is measured in weeks, not hours. Checking daily is normal; changing settings daily is counterproductive.

You can see each mailbox's current spam share and inbox placement on your Warmup page. If a mailbox has been reduced for more than about three weeks with clean authentication and no cold sending, email [email protected] with the mailbox address and we will take a look at that specific mailbox for you.

What reduced volume is not

It is not a pause, a penalty, or anything you have lost. Specifically:

• It is not a pause. Warmup is still running on that mailbox — just at a smaller daily amount. The mailbox stays connected and nothing needs switching back on.
• Your campaigns are not affected. Reduced warmup volume applies to warmup only. Your cold email campaigns keep sending, and your LinkedIn and Instagram outreach are separate and untouched. (That said, if a mailbox is being filtered, easing off cold sending from it is a good idea anyway — see the checklist above.)
• Your warmup progress is kept. Your history and the ramp you have built stay where they are. Volume resumes from there.
• It is not a punishment for something you did wrong. Deliverability moves around for all sorts of ordinary reasons. This is a guard-rail doing its job, not a judgement.
• It is not the same as your mailbox being blocked. Nothing is blocked or suspended. The mailbox is simply sending less warmup for a while.

How this differs from a pause, a ramp, or Recovery

Several warmup states can produce "fewer emails than I expected", and they mean different things:

• Reduced volume (this page) — warmup is running but sending less, because too much of this mailbox's warmup mail has been landing in spam. Lifts on its own as placement recovers.
• The normal ramp — a new mailbox starts small on purpose and grows over its first weeks. Nothing is wrong; this is how every mailbox begins. See How email warmup ramps up.
• Warmup paused — warmup has stopped on that mailbox entirely, either as a short delivery precaution or because of a billing issue. See Why your warmup can pause — and how it resumes.
• Recovery — a gentler ramp a mailbox can move onto when its inbox placement dips, easing volume down and then lifting it back toward your target on its own. It is a slower-moving, separate mechanism from the volume reduction described on this page, and the two can overlap.
• A partial day — warmup spreads each day's emails across the whole day, so the count always looks small in the morning and fills in by evening. See Why does my warmup show only a few emails sent earlier in the day?

If you are unsure which you are looking at, check whether warmup is switched on for that mailbox. If it is on and sending a small number, it is the ramp or reduced volume. If it is off, it is a pause.

Frequently asked questions

Why did my warmup volume suddenly drop?

Because some of that mailbox's warmup emails have been landing in spam rather than the inbox, so WarmySender has eased its daily warmup volume back while placement recovers. Sending more mail from a mailbox that is currently being filtered teaches providers, at volume, that your mail is the kind to filter — so reducing volume protects the reputation you are building. It affects warmup on that one mailbox only, your campaigns keep sending, and the volume lifts again on its own as placement improves.

Is it because my mailbox is bad, or because it is new?

It can be either, and they are treated differently. If only a small amount of warmup mail has been placed so far, there is not enough to judge the mailbox on, so it gets a small daily allowance to build up a real picture — usually a few days to about a week, and you do not need to do anything. If plenty has been placed and too much of it is being filtered, that is a genuine answer about the mailbox and volume drops further while its reputation is protected — usually one to three weeks, and there is normally an underlying cause worth fixing, starting with your domain's SPF, DKIM and DMARC records.

How much spam is too much?

Roughly one in twenty — about 5% of a mailbox's warmup emails landing in spam instead of the inbox, measured over the last week. Below that, the mailbox warms at its normal pace. At or above it, volume is reduced while placement recovers. There is a second, higher line at roughly 15%, above which the mailbox is also kept out of the pool that other people's warmup is sent to, so a struggling mailbox is never asked to carry someone else's reputation. Only warmup activity is measured — your campaign opens, replies and bounces are tracked separately and never feed into it.

My mailbox only sent two warmup emails and one went to spam. Is that really a 50% spam rate?

On paper, yes — but it is not a meaningful one, and WarmySender does not treat it as a verdict. A single filtered message out of two tells you almost nothing; healthy mailboxes have days like that. Fifty out of a hundred is the same percentage but a completely different fact. So the system waits until it has enough placements to be confident before concluding anything, and in the meantime gives the mailbox a small daily allowance so it can build up a real run of results and earn a proper answer. That allowance is always capped by the mailbox's normal ramp for its age, so it never sends more than a healthy mailbox of the same age would.

How long does reduced warmup volume last?

If it is the "still building a picture" state, usually a few days to about a week — just long enough for the mailbox to place enough warmup mail for the answer to become clear. If the mailbox really is landing in spam, it lasts until its placement over the last week comes back under the line, which is typically one to three weeks once the underlying cause is fixed. In both cases it lifts on its own; there is no button to press. Because the measurement covers the last week, changes show up gradually rather than instantly.

What should I do to fix it?

Leave warmup running, then check your domain's SPF, DKIM and DMARC records first — missing, duplicated or incorrect authentication is by far the most common cause. Next, ease off cold sending from that specific mailbox, since warmup and campaigns share the same reputation and pushing cold volume works against the recovery. Then consider the domain's history: a second-hand domain can arrive with a reputation already attached. Finally, give it time — warmup recovery is measured in weeks. The one thing not to do is switch warmup off or remove and re-add the mailbox: that resets nothing and removes the mailbox's only route back, because it needs to keep placing warmup mail to prove it is healthy again.

Will I lose my warmup progress?

No. Reduced volume is not a reset. Your warmup history and the ramp you have built stay exactly where they were, and when volume lifts it continues from there rather than starting at day one. Nothing is deleted and the mailbox stays connected throughout.

Does this stop my campaigns?

No. Reduced warmup volume applies to warmup on that one mailbox. Your cold email campaigns keep sending, and your LinkedIn and Instagram outreach are separate and unaffected. That said, if a mailbox's warmup mail is being filtered, its campaign mail is likely getting the same treatment — so easing off cold sending from that specific mailbox while it recovers is worth doing, even though nothing forces you to.

Should I disconnect and reconnect the mailbox, or delete and re-add it?

No — and this is the most common mistake. Reconnecting or re-adding a mailbox does not clear a reduced volume state, because the state reflects how your mail has actually been landing over the last week, not a setting stored against the mailbox. What it does do is interrupt the warmup activity the mailbox needs in order to demonstrate that it is healthy again, which makes the reduction last longer. Leave the mailbox connected, leave warmup on, and fix the underlying cause instead.

All of my mailboxes on one domain were reduced at once. What does that mean?

That points at a domain-level cause rather than anything specific to an individual mailbox — most often SPF, DKIM or DMARC records that are missing, duplicated or incorrect, or a domain that arrived with an existing reputation. Check the domain's authentication records first, and confirm they are correct and passing. If one mailbox out of several on the same domain is affected while the others are fine, the cause is more likely specific to that mailbox — how it is sending, or how much cold volume has been pushed through it.

Related reading

• How to control your warmup sending volume — setting a daily target and choosing a ramp speed
• How email warmup ramps up — what to expect in your first hour, first day and first week
• Why your warmup can pause — and how it resumes — when warmup stops entirely rather than slowing down
• What is my mailbox's warmup score? — how inbox placement, spam and bounces roll into one number
• Why does my warmup show only a few emails sent earlier in the day? — the normal partial-day count
• My sending domain shows on a blocklist — when the cause is external to your mailbox
• Email Warmup FAQ — how warmup builds and protects mailbox reputation
• Your warmup — see spam share, inbox placement and daily volume per mailbox
• Full documentation — Cold Email, Email Warmup, LinkedIn, Instagram and Multichannel guides