---
title: Inbox placement
description: Delivery is a 200 OK from an SMTP server. Placement is whether the recipient actually sees the message.
---

## Delivery vs placement

Most cold-email tools report "delivery rate": the percentage of messages that the receiving SMTP server accepted. That number is almost always close to 100% and tells you almost nothing.

A receiving server can accept a message (delivery) and then immediately filter it into Spam, Promotions, or out of the inbox entirely. Placement is the share of accepted messages that land in the recipient's primary inbox.

The two numbers can be wildly different. 99% delivery and 30% placement is not unusual on a poorly authenticated cold mailbox.

## How placement is measured

### Warmup probes

Warmbly's [warmup pool](/learn/warmup-pools/) is also a placement probe. Pool members report where each warmup message arrived: inbox, spam, or promotions. We aggregate per sending mailbox over a rolling sample window.

Probe accuracy depends on pool diversity. A pool that only contains Gmail addresses can't tell you anything about Outlook placement. Our premium pool spans Gmail, Outlook, Yahoo, iCloud and self-hosted IMAP servers in proportion to the broader receiver landscape.

### Seed lists

Some teams maintain a "seed list": a fixed set of mailboxes across providers that always receive a copy of every campaign send. The placement on the seed list approximates placement for the full campaign.

Seed lists are useful but not free of bias. They tend to be older, more engaged inboxes than your real cold recipients. Treat them as a directional signal.

### Recipient feedback

If a recipient moves a message from Spam to Inbox, replies, or adds you to their address book, the provider sometimes tells you (through FBL feeds or workspace integrations). These are the strongest individual signals.

## What hurts placement

- Unauthenticated mail (missing or misaligned [SPF, DKIM, DMARC](/learn/spf-dkim-dmarc/)).
- Sudden volume spikes from an otherwise quiet mailbox.
- Cold mail with heavy HTML, unsolicited attachments, or tracking-pixel-only bodies.
- Word-for-word identical content across thousands of sends: content fingerprinting catches it.
- Long URLs to suspicious TLDs, or URL shorteners that have been abused.
- Recipients consistently deleting without opening.
- Recipients marking as spam (the worst signal of all).

## What helps placement

- Plain text bodies for cold sequences.
- Sensible volume relative to historical baseline for the mailbox.
- Real replies from real recipients. This is the strongest positive signal.
- Variation in subject and opening line across recipients.
- Tight, well-targeted contact lists. Sending to obviously-bad addresses (parsed from web pages, role accounts, etc.) inflates bounces and complaint risk.
- A consistent sending pattern: same business hours every day, with weekends off.

## Targets to aim for

| Inbox placement | What it means |
| --- | --- |
| Above 90% | Healthy mailbox. |
| 80-90% | Acceptable, but watch for drift. |
| 60-80% | Something is wrong. Audit auth, content, volume. |
| Below 60% | Stop campaigns from this mailbox. Investigate immediately. |

## Why we don't lead with open rate

Apple's Mail Privacy Protection pre-fetches images on the recipient's behalf, generating a "fake" open for every message regardless of whether the human actually looked. Gmail caches images aggressively, producing repeated "opens" or none at all depending on cache state.

The result: open-rate dashboards report numbers that bear no consistent relationship to actual reads. Warmbly surfaces opens for situational use, but we don't use them in deliverability decisions.

<Callout type="info" title="Placement is a leading indicator">
  Reply rate is a trailing one. If your placement starts to slip and you only watch replies, you'll notice the problem about three weeks too late.
</Callout>
