Understanding your warmup Inbox Rate

Your Inbox Rate is the share of your verified warmup emails that landed in the inbox instead of the spam folder. In plain terms: of the warmup emails WarmySender was able to scan and confirm placement for, what percentage reached the inbox. Emails we couldn't scan are "unverified" — they aren't counted for or against your Inbox Rate, so the number always reflects real, confirmed placement. This page explains exactly how the rate is calculated, what the "Verified X% of sent" figure next to it means, and why the headline number on your warmup dashboard and the per-mailbox numbers in the table now always agree.

WarmySender is a 4-pillar outreach platform — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel sequences. This guide covers an Email Warmup question: how to read your Inbox Rate.

What "Inbox Rate" means

Every warmup email your mailbox sends is part of a real peer-to-peer conversation with another mailbox in the network. When that email arrives, WarmySender looks in the receiving mailbox to see where it landed — the inbox, or the spam folder. That check is what lets us measure your placement.

Your Inbox Rate is simply:

So an Inbox Rate of 98% means that, out of every 100 warmup emails whose placement we confirmed, 98 reached the inbox and 2 went to spam. It's a quality measure: among the mail we can actually see, how much of it is landing where you want it to.

Why some emails are "unverified"

We can't always scan the receiving mailbox to confirm where a warmup email landed. There are normal, everyday reasons for this — the receiving mailbox might still be syncing, the message might be in transit, or it simply hasn't been scanned yet at the moment you're looking. Those emails are counted as unverified.

Here's the important part: unverified emails are not counted for or against your Inbox Rate. An email we couldn't confirm is neither a win nor a loss — it's set aside entirely. We never assume an unverified email went to spam, and we never assume it reached the inbox. Your Inbox Rate is built only from emails whose placement we actually confirmed, so it always reflects real results rather than guesses.

Seeing some unverified warmup mail is completely normal, especially early in the day or right after warmup starts on a new mailbox. It does not mean anything is wrong, and it does not pull your Inbox Rate down.

What "Verified X% of sent" means

Next to your Inbox Rate you'll see a second figure — something like "Verified 90% of sent." This is your coverage: the share of all warmup emails sent that we were able to scan and confirm placement for.

Coverage answers a different question than Inbox Rate. Inbox Rate tells you how good your placement is among the mail we can see; coverage tells you how much of your sent mail we were able to check. A high coverage number means your Inbox Rate is based on a large, representative sample. As warmup runs through the day, coverage naturally climbs as more emails finish arriving and get scanned.

A worked example

Numbers make this concrete. Say 100 warmup emails were sent from your mailbox, and WarmySender could verify the placement of 90 of them. Of those 90, 89 landed in the inbox and 1 went to spam. The other 10 were still unverified at the time you checked.

Measure How it's calculated Result
Warmup emails sent — 100
Verified (inbox + spam) 89 + 1 90
Unverified (set aside) 100 − 90 10
Inbox Rate 89 ÷ 90 98.9%
Verified coverage 90 ÷ 100 90%

Notice that the 10 unverified emails never entered the Inbox Rate math at all — the rate is 89 ÷ 90, not 89 ÷ 100. That's what keeps the number honest: it measures placement among confirmed mail, and reports separately how much of your mail was confirmed.

Why your inbox rate can look low when you're sending only a few emails

Your Inbox Rate is just a ratio: of the warmup emails we could verify, how many landed in the inbox instead of spam. When that ratio is built from only a handful of emails, a single email can swing the percentage dramatically — so a low (or high) number from a tiny sample isn't a real signal about your deliverability. It's just a small sample.

For example, if only 3 warmup emails have been measured and 2 landed in the inbox, that shows as 66% — but a single email moves the number by 33 points. One more inbox email would jump it to 100% (3 of 3); one spam email instead would drop it to 50% (2 of 4). The placement didn't really change that much — there just aren't enough emails yet for the percentage to mean anything.

A reliable reading needs roughly 20 or more measured warmup emails. Below that, one email landing differently can move the percentage by 5 points or more, so the number bounces around without telling you anything useful. That's why, until enough emails have been measured, your dashboard shows a "building data" note instead of leaning on a percentage we don't yet trust ourselves.

Low daily volume is on purpose — and the swing that comes with it is expected. During low-volume stretches — for example while a new mailbox is gently ramping up, or while an older one is carefully rebuilding trust — only a small number of warmup emails go out each day by design. That protects your sending reputation, but it also means the day-to-day percentage will swing more, simply because each day's sample is small. A 100% one day and an 80% the next, on just a few emails each, is normal — it isn't a failure or a sign something broke.

The good news: this fixes itself. As warmup keeps running and daily volume grows, the sample behind your Inbox Rate gets larger, the number settles down, and it becomes genuinely meaningful. The right way to read it is to watch the trend over a couple of weeks, not to react to a single day — especially a single low-volume day.

Why the headline number and the per-mailbox numbers now always agree

On your warmup dashboard you'll see an Inbox Rate at the top (the headline number across all your mailboxes) and an Inbox Rate next to each individual mailbox in the table below. These now always use the exact same formula — inbox ÷ (inbox + spam), with unverified mail excluded everywhere.

Previously, the headline number could read lower than the per-mailbox numbers on the same screen, which understandably looked confusing — "which one is real?". The per-mailbox number was always the honest one. The headline used to quietly count unverified mail against the rate, which dragged it down on mailboxes that had a lot of mail still waiting to be scanned. We fixed that so every surface measures placement the same way. If you ever see the top-of-page rate and a mailbox's rate disagree in a way the verified-coverage figures don't explain, that's worth reporting to us.

What a healthy result looks like

A healthy warmup mailbox shows a high Inbox Rate and a low spam share — most established mailboxes settle in the high 90s for Inbox Rate, with spam at a percent or two. Alongside that, it's completely normal to see some unverified mail at any given moment; coverage rises over the course of the day as more emails finish arriving and get scanned.

If you want to improve a low Inbox Rate, the durable levers are the same ones that improve all deliverability: confirm SPF, DKIM, and DMARC are set up correctly on your sending domain, keep your real sending content natural, and let warmup keep running so your reputation builds over time. See our deliverability resources for a step-by-step setup, and how warmup ramps up for what to expect week by week.

Frequently asked questions

How is my Inbox Rate calculated?

Your Inbox Rate is the number of warmup emails that landed in the inbox divided by the number of warmup emails we could verify (inbox plus spam), shown as a percentage. Emails we couldn't scan to confirm placement are "unverified" and are left out of the calculation entirely — they're neither counted as inbox nor as spam. So if 90 of your warmup emails were verified and 89 of those reached the inbox, your Inbox Rate is 89 divided by 90, which is 98.9%. The rate always reflects confirmed placement, never guesses.

Why are some of my warmup emails "unverified"?

Because WarmySender can't always scan the receiving mailbox to confirm where a warmup email landed at the exact moment you're looking. Common reasons are completely normal: the message is still in transit, the receiving mailbox is still syncing, or the email simply hasn't been scanned yet. Unverified emails are set aside — they do not count for or against your Inbox Rate. Seeing some unverified mail is normal, especially early in the day or soon after warmup starts on a new mailbox, and it doesn't mean anything is wrong.

Do unverified emails lower my Inbox Rate?

No. Unverified emails are excluded from the Inbox Rate math completely. We never assume an unverified email went to spam, and we never assume it reached the inbox — it's simply not counted. Your Inbox Rate is built only from emails whose placement we actually confirmed, so a batch of unverified mail will not drag the number down. It only affects your "Verified % of sent" coverage figure, which rises as more of your mail gets scanned.

Why is my Inbox Rate low when it's based on only a few emails?

Because a small sample swings hard. Your Inbox Rate is just the share of measured warmup emails that landed in the inbox, so when only a handful have been measured, a single email moves the percentage a lot. For example, if only 3 warmup emails have been measured and 2 landed in the inbox, that shows as 66% — but one more inbox email jumps it to 100% (3 of 3), and one spam email instead drops it to 50% (2 of 4). That's not a real signal about your deliverability; it's just a tiny sample. A reliable reading needs roughly 20 or more measured warmup emails, which is why your dashboard shows a "building data" note until then. Low daily volume is also normal and protective — while a mailbox is gently ramping up or rebuilding trust, only a few warmup emails go out each day on purpose, so the percentage naturally swings more day to day. It settles down and becomes meaningful as volume grows, so watch the trend over a couple of weeks rather than any single day.

What does "Verified X% of sent" mean?

That's your coverage — the share of all the warmup emails you sent that WarmySender was able to scan and confirm placement for. For example, "Verified 90% of sent" means we confirmed where 90% of your sent warmup emails landed; the remaining 10% were still unverified when you checked. Coverage tells you how large the sample behind your Inbox Rate is, while the Inbox Rate itself tells you how good the placement is within that sample. Coverage naturally climbs through the day as more emails finish arriving and get scanned.

Why did the Inbox Rate at the top of the page differ from the per-mailbox number before?

It used to differ because the headline number quietly counted unverified mail against the rate, while the per-mailbox number didn't — so on mailboxes with a lot of mail still waiting to be scanned, the headline read lower. The per-mailbox number was always the honest one. We've fixed this: every Inbox Rate on the dashboard now uses the same formula, with unverified mail excluded everywhere, so the headline figure and the per-mailbox figures always agree. If they ever disagree in a way the verified-coverage figures don't explain, please let us know.

What's a healthy Inbox Rate?

For an established mailbox, a high Inbox Rate — typically in the high 90s — with a low spam share is what you want to see. It means almost all of your verified warmup emails are landing in the inbox rather than spam. A brand-new mailbox may take a couple of weeks to climb there as warmup builds its reputation. Alongside a healthy rate, it's normal to see some unverified mail at any given moment; that doesn't count against you. If your Inbox Rate is lower than you'd like, confirm SPF, DKIM, and DMARC on your sending domain, keep your content natural, and let warmup keep running.

Reporting a problem with your Inbox Rate

If your Inbox Rate doesn't look right — for example, the number at the top of the page disagrees with a mailbox's number in a way the verified-coverage figures don't explain — please tell us. We want every number on your dashboard to be one you can trust.

Email [email protected] with the mailbox address and a screenshot of the warmup dashboard showing the numbers you're asking about.

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