Use a verified Resend domain and a sending-only API key to pace warmup messages and check inbox placement from the same sender.

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## Prepare the sender in Resend

1. Add the sending domain or subdomain under **Domains** in Resend.
2. Publish the DNS records Resend supplies and wait for its verified status. Use the exact record names for your subdomain; keep existing inbound mail records in place.
3. Under **API Keys**, create a key with **Sending access** and restrict it to the verified domain.
4. Save the key securely when it is displayed. Choose a From address on that domain.

Use an account approved for your intended sending, and include production traffic when checking provider limits. See [Resend API key management](https://resend.com/docs/dashboard/api-keys/introduction) for provider setup details.

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## Connect and verify in MailSlurp

Open **Email warmup > Create warmup** or **Inbox placement > Automations > Create automation**. Select **Resend** in the sender step, or reuse the existing verified connection for that sender.

Enter a recognizable connection name, sender name and authorized From address, followed by these values:

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| Field | Value |
| --- | --- |
| Connection type | Resend API key |
| Credential | Sending-access API key restricted to the sending domain |
| From address | An address on that verified domain |

Choose **Verify and continue** and complete the delivery test before proceeding. Check credential verification and the received test separately: an authenticated connection does not by itself prove message delivery. Reuse this connection for both features instead of creating another copy of the same sender.

## Schedule automated inbox placement

1. Open [Inbox placement automations](https://app.mailslurp.com/inbox-placement/automations/) and select **Create automation**.
2. Select the verified Resend connection.
3. Set the schedule name, **Frequency** and **Inbox audience**. Account allowance and provider limits must cover every seed recipient in each run.
4. Enter the subject and text body, retaining `{{trackingToken}}` in at least one of them. MailSlurp substitutes a fresh marker for each test.
5. Select **Create automation**, then inspect the saved schedule and next run.
6. Use **Run now** for an immediate check if needed. Inspect a later scheduled execution separately to confirm the recurrence is working.

Open the linked report and wait for all targets to settle. Compare inbox, provider tabs, spam and not-received results with the same messages in Resend's activity. A provider delivery event does not prove inbox placement. Pausing the schedule stops future scheduled tests while preserving its history.

The scheduled subject and text body are the message being tested. To check a finished campaign with different HTML, links or routing, use the [manual placement workflow](/docs/inbox-placement/) through the original sending path.

## Start and monitor warmup

Open **Email warmup > Create warmup** and choose the same connection. Set the sender goal, ramp preset or custom daily volumes, time zone and sending window. Select managed content or an allowed custom subject and plain-text body. Review the resolved coverage and estimated usage before starting.

Controlled coverage measures paced delivery to managed inboxes. Core coverage adds provider placement checkpoints when your plan and the available coverage permit them. Review accepted sends, observed controlled receipts and completed checkpoint folders separately; a progress percentage alone does not establish successful delivery.

Choose maintenance when you want ongoing activity after the ramp. For a finite program, disable maintenance and follow the remaining ramp and any final checkpoint through its terminal state. Pause while investigating a persistent send failure, then resume the existing program after correcting it. A short successful run does not establish a lasting reputation improvement.

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## Review capacity, usage and errors

Warmup and placement automation share a Delivery Sender allocation. Creating or verifying a connection does not consume an enabled sender seat; starting a workflow can enable it. Pausing retains the allocation. After stopping warmup and pausing all automations that use it, disable the sender in **Settings > Sending connections** if you want to release that capacity.

Read the account's included allowance and credit weights before sending. Warmup uses weighted message credits; standalone and automated placement use placement-test allowance. Warmup placement checkpoints use warmup credits rather than consuming another standalone placement test. Provider recipient limits still apply to every message.

A restricted key must cover the exact domain of the From address. If Resend accepts a message but the recipient has not received it, inspect the message in Resend Emails and compare the recipient with the MailSlurp result. Delivery to a mail server does not identify its inbox folder.

See [warmup configuration and results](/docs/email-warmup/) for pacing and program controls, and [placement automation and reports](/docs/inbox-placement-automation/) for API workflows and exports.