What is my mailbox's warmup score?

Your warmup score is a simple, at-a-glance read on how healthy a mailbox is for sending right now. In plain terms, it reflects how well your recent warmup mail has been landing in the inbox — rather than spam — with steady, reliable sending and very few messages bouncing. It looks at roughly the last week or so of activity, so it's always a picture of how your mailbox is doing lately, not months ago. A high score means your recent inbox placement has been strong and the mailbox is in good shape to send from; a lower score is a gentle nudge that your recent placement could be better and warmup should keep building it. This page explains what the number means, why a new mailbox shows "Building data" instead of a score, why a score recovers on its own after a rough patch, and how to tell when a mailbox is safe to send from.

WarmySender is a 4-pillar outreach platform — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel sequences. This guide covers an Email Warmup question: what your mailbox's warmup score means and how to read it.

What the score actually measures

Warmup works by quietly exchanging friendly emails between real inboxes and checking, for each one, whether it landed in the inbox or in spam. Your warmup score is built from that recent track record. Three things move it:

• Inbox placement — the share of your recent warmup mail that landed in the inbox rather than spam. This is the biggest factor, because it's the clearest sign that inbox providers trust your mailbox. For a deeper look at just this part, see Understanding your warmup inbox rate.
• Steady, clean sending — mail that goes out reliably and reaches real inboxes, without messages coming back undelivered.
• Recency — the score leans on your recent activity, so it always reflects how the mailbox is behaving now, and older history gradually fades out of the picture.

You don't need to calculate anything or tune any settings — WarmySender works the score out for you and keeps it up to date as your warmup runs. You'll find it on the Warmup page next to each mailbox.

Why a brand-new mailbox shows "Building data"

When you first connect a mailbox, you'll often see "Building data" where a score would go, instead of a number. That's on purpose, and it's a good thing: a score only means something once there's enough recent activity behind it. In the first day or two, warmup simply hasn't sent and checked enough mail yet to say anything reliable, so putting a number there would be little more than a guess — and a guess is exactly what you don't want to make a sending decision on.

So rather than show you a number we can't stand behind, WarmySender shows "Building data" until there's a solid base to score from. Give a new mailbox a few days of warmup and a real score appears on its own. This is completely normal for every new mailbox, and it lines up with how warmup starts gently and ramps up — see How email warmup ramps up for what to expect in your first hour, day, and week.

Why a score climbs back after a rough patch

Because the score is built from your recent activity, it recovers naturally once things are going well again — you don't have to do anything to "reset" it. If a mailbox had a rough stretch (say some warmup mail slipped into spam for a few days, or the mailbox briefly couldn't send), the score dips to reflect that. But as fresh, healthy days come in, the older rough days gradually age out of the window the score looks at, and the number climbs back up on its own.

This is why the best thing to do after a rough patch is usually to simply let warmup keep running. Steady, healthy recent activity is exactly what pulls the score back up. There's nothing to remove and re-add, and no setting to change — recent good behaviour replaces the old, and the score follows.

Is it safe to send from this mailbox?

A mailbox that's scoring high, with steady inbox placement, is in good shape to send from — that's exactly what a strong warmup score is telling you. If you're deciding whether to send a campaign from a particular mailbox, a high, steady score is a green light.

• High and steady — great to send from. Your recent mail has been landing well, which is the sign inbox providers trust it.
• "Building data" — not a warning, just early days. Let warmup run a little longer before leaning on that mailbox for a big campaign; it'll earn a real score soon.
• Lower than you'd like — keep warmup running and give it time. A lower score is a signal to let the mailbox build more before pushing volume through it, not a sign that anything is broken. Warmup is designed to bring it up.

Warmup also protects you automatically while it works — it steers around inboxes that aren't accepting mail so your reputation isn't spent on messages that would bounce. You can read how that works in How WarmySender protects your deliverability.

A quick example

Say you have three mailboxes:

1. One you connected two weeks ago that's been warming nicely — almost all of its warmup mail has been landing in the inbox, very little marked as spam, and nothing bouncing. It shows a high score. This is a mailbox you can confidently send a campaign from.
2. One you added yesterday. It shows "Building data" — not because anything's wrong, but because there simply isn't enough recent activity yet. Give it a few days and a real score appears.
3. One that had a rough week — a stretch where some warmup mail slipped into spam — so its score dipped. You leave warmup running, and over the following days its fresh, healthy activity replaces the older rough days. Without you touching anything, the score climbs back up.

Same platform, three honest pictures — each one based on what that mailbox has actually been doing lately.

Why the number moves a little day to day

Your warmup score updates as warmup runs, so it's normal for it to move up or down a little from one day to the next — especially on a day when a mailbox sent or received less than usual (for example while it was briefly reconnecting). A small wobble isn't something to worry about. The most reliable way to read your warmup health is the trend over a couple of weeks rather than any single day. If the trend is steady or climbing, you're in good shape.

Frequently asked questions

What is my warmup score and what does it mean?

It's a simple read on how healthy a mailbox is for sending right now, based on how well your recent warmup mail has been landing in the inbox (rather than spam), with steady, low-bounce sending. It reflects roughly the last week of activity, so it always shows how the mailbox is doing lately. A high score means your recent inbox placement has been strong; a lower one means warmup should keep building it up.

Why does my new mailbox say "Building data" instead of a score?

Because a score only means something once there's enough recent activity behind it. A brand-new mailbox hasn't sent and received enough warmup mail yet to score reliably, so instead of showing a number we can't stand behind, WarmySender shows "Building data". Give it a few days of warmup and a real score appears on its own. It's completely normal and not a sign of any problem.

My score was low and now it's higher — what changed?

The score is built from your recent activity, so it recovers on its own as healthy days come in. If a mailbox had a rough patch, the older rough days gradually age out of the window the score looks at, and fresh, healthy activity takes their place — so the number climbs back up without you doing anything. Letting warmup keep running is exactly what brings it back.

Is a high score safe to send from?

Yes. A mailbox scoring high with steady inbox placement is in good shape to send from — that's what the score is telling you. If the mailbox shows "Building data", it's just early days: let warmup run a little longer before leaning on it for a big campaign. If the score is lower than you'd like, keep warmup running and give it time to build before pushing more volume through that mailbox.

Why does the number move a little day to day?

Your score updates as warmup runs, so small day-to-day movement is normal — particularly on a day when a mailbox sent or received less than usual. A little wobble isn't a concern. Read the trend over a couple of weeks rather than a single day; if it's steady or climbing, you're in good shape.

How do I improve my warmup score?

Keep warmup running steadily and let it do its job — that's the main thing. A mailbox that stays connected and warms consistently builds the recent track record of good inbox placement that lifts the score. There's no setting to tweak; warmup gradually raises your reputation for you. Avoid suddenly blasting a large volume from a mailbox that's still early in warmup, and let new mailboxes ramp up before leaning on them.

Does a lower score mean my mailbox is broken or my domain is blocked?

No. A lower score just reflects your recent inbox placement and means warmup has more building to do — it's not a verdict that anything is broken or blocked. The score is designed to move, and warmup is designed to bring it up over time. Keep warmup running and read the trend over a couple of weeks rather than reacting to a single day.

Where do I see my warmup score?

On the Warmup page, next to each mailbox. You'll see the score (or "Building data" for a very new mailbox) alongside your inbox placement and other warmup details, so you can tell at a glance which mailboxes are in good shape to send from.

Related reading

• Understanding your warmup inbox rate — the inbox-placement number that's the biggest part of your score
• How email warmup ramps up — what to expect in your first hour, first day, and first week
• Warmup shows active but no emails are arriving — why incoming warmup can briefly pause and recover on its own
• How WarmySender protects your deliverability — how warmup steers around inboxes that aren't accepting mail
• Email Warmup FAQ — how warmup builds and protects mailbox reputation across the network of senders
• Your mailboxes — check connection and warmup status per mailbox
• Full documentation — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel guides