Email campaigns with Resend

Overview

Email campaigns connect MailTooth's verification and delivery workflows. A campaign always begins with a bulk verification job that has downloadable results. You choose the result set and recipients, review names, compose the message, select the Resend route, and confirm that you may contact the audience before the job is queued.

Verified source

Keep the campaign tied to the bulk job and result file that produced its audience.

Recipient personalization

Use first name, last name, and email variables in the subject and plain-text message.

Flexible delivery

Send through one Resend account or distribute recipients across multiple selected accounts.

What campaign progress representsAn accepted recipient means Resend accepted the send request. It does not guarantee inbox delivery and does not represent an open or click. Use Resend and your normal deliverability tooling for later delivery events, bounces, complaints, unsubscribes, and engagement.

Before you begin

You need all of the following before creating a campaign:

A Resend account with a sending domain and From address that Resend permits you to use.
A Resend API key intended for sending. Treat the complete key as a secret and use a separate key for each connection when possible.
A completed, partial, or stopped MailTooth bulk verification job whose result files are still available. See the bulk verification guide.
Permission or another lawful basis to contact every recipient, plus the unsubscribe and identity information required for your use case.
Bulk verification permission in the workspace. Managing Resend connections also requires API-key management permission.

Connect Resend

Open Dashboard → Integrations.
Under Email delivery, add an account for Resend.
Enter a recognizable account name and paste the Resend API key.
Enter the approved From email and an optional From name, then choose Connect account.

Encrypted credential

The API key is encrypted at rest and is never returned after saving; only its final four characters remain visible.

Named sender

Each connection stores its own recognizable name, From address, and optional From name.

Multiple accounts

Add several Resend accounts and choose the exact connection or connections for each campaign.

A connection used by a queued or processing campaign cannot be edited or disconnected. Wait until the campaign reaches a terminal status. Disconnecting later preserves existing campaign history.

Prepare the campaign audience

Run a bulk verification jobfor the CSV or TXT audience, using the depth appropriate for the send.
Wait for results, then open Email campaigns → Create campaign.
Select the source job. Only jobs with available result files are shown.
Choose Verified only for the safest default, or All results to inspect other sendable records.
Send to all eligible records or pick recipients. Selections are preserved while you page through the preview.

Review “All results” carefullyThis set can contain risky, unknown, and failed-verification records. Malformed addresses cannot be selected, but a syntactically sendable address may still bounce. Prefer verified-only unless you understand and accept the additional risk.

Compose and launch a campaign

Enter an internal campaign name. It appears in campaign history and is not included in the recipient's message.
Add an optional Reply-to address, then write the subject and plain-text message.
Select a single account or configure round-robin delivery.
Confirm that the audience consented or that you otherwise have a lawful basis to send the message.
Queue the campaign. The audience, message, and route are captured and delivery begins asynchronously.

Field	Purpose	Limit or behavior
Campaign name	Internal label	Required · 200 characters
Reply-to	Where replies are directed	Optional · valid email
Subject	Recipient-facing subject	Required · 998 characters
Message	Recipient-facing body	Required · plain text
Audience	Resolved recipients	1 to 10,000 recipients

Review everything before queuing. The current workflow does not offer drafts, scheduling, pause, cancellation, or resend actions after launch.

Personalize the subject and message

The subject and message support three case-insensitive variables. Spaces inside the braces are allowed. When a name is unavailable, its variable renders as an empty string, so make sure the sentence still reads naturally.

Variable	Value
`{{first_name}}`	Recipient first name
`{{last_name}}`	Recipient last name
`{{email}}`	Normalized recipient email

Plain-text message

Hi {{first_name}},

We wanted to share an update with you.

This message was sent to {{email}}.

Best,
The Northstar team

Correct first and last names in the audience table before launch. Overrides apply only to this campaign and do not rewrite the original bulk result file.

Choose a delivery route

Strategy	Accounts	Behavior
Single account	Exactly one	Every recipient is sent through the selected Resend connection.
Round robin	Two or more	Recipients are assigned deterministically and spread evenly across the selected connections.

Every account remains subject to its own Resend quota, domain configuration, and sending policies. If one round-robin account fails a batch, MailTooth records those recipients as failed and continues processing groups assigned to the other accounts.

Round robin is routing, not automatic quota or reputation management. Do not use multiple accounts to evade provider limits or policies.

Monitor status and results

Open Email campaigns to see audience size, progress, creation time, and accepted and failed counts. An active campaign page refreshes while work is queued or processing.

Status	Meaning
Queued	The campaign was created and is waiting for a worker.
Processing	Recipient batches are being submitted to Resend.
Completed	Resend accepted every recipient send request.
Partial	At least one request was accepted and at least one failed.
Failed	No recipient was accepted, or delivery stopped before any success.

Progress is the percentage processed as accepted or failed. The detail page also preserves the source file, subject, message, delivery strategy, and sender identities used by the campaign.

Send responsibly

Send only to people you may lawfully contact. Verification confirms address signals; it does not create consent.
Identify the sender and provide the disclosures and unsubscribe path required for your message type and recipients.
Monitor Resend's downstream bounce and complaint signals and adjust future sends if reputation indicators deteriorate.
Keep volume consistent with your account history, domain reputation, and provider limits.
Do not treat verification or provider acceptance as proof that a person requested or read the message.

Troubleshooting

Symptom	Likely cause	What to do
No verification jobs appear	No eligible job has result files available.	Complete a bulk job or use a newer job whose retention period has not ended.
No sending account appears	Resend is not connected in this workspace.	Add a connection and confirm its From address is allowed by Resend.
Round robin cannot continue	Fewer than two accounts are selected.	Select two distinct connections or use single-account delivery.
Recipient count is zero	The result set has no eligible address or no picked recipient.	Use a sendable result set or select at least one eligible recipient.
Campaign is partial	Some Resend requests were accepted and others failed.	Review sender configuration and provider limits before a follow-up.
Connection cannot be edited	A queued or processing campaign is using it.	Wait for a terminal campaign status, then try again.

Create an email campaign