Connect your app to Resend

Resend provides email delivery for applications. Connect your account to Mythos to build email into purchases, bookings, signups, and other moments in your app. Messages are sent through your Resend account, using a domain you have verified there.

Resend works as an App + chat connector. You can use the connection in project chat while building and in the app you publish. See Connections in Mythos for the shared connection settings.

Your app can use Resend to:

Compose messages in HTML or plain text.
Email one or several recipients, including CC, BCC, and a reply address.
Include attachments and add tags to organize sending activity.
Look up sending domains and the delivery status of sent messages.

Examples to build

Ask Mythos to build the email workflow your app needs. These prompts give you a starting point.

App idea	Prompt to try	What it adds
Purchase emails	“After an order is paid, email the buyer a receipt with Resend.”	Send after a purchase. Your app emails a receipt through Resend when payment is complete, including the customer’s order details.
Appointment updates	“Use Resend to notify the attendee and my studio when a session is booked.”	Keep customers and staff informed. A new booking sends the attendee a confirmation and gives your studio a copy of the appointment details.
Welcome and follow-up	“Create a Resend welcome email for new members and schedule a getting-started email for two days later.”	Help new members get started. The signup flow sends a welcome immediately and schedules a second message with tips for two days later.
Subscriber updates	“Build a mailing-list signup and let me send product updates with Resend.”	Turn signups into a mailing list. The app saves subscribers and lets you send product campaigns through Resend from your verified domain.
Priority alerts	“Email our sales team through Resend when a new order is worth more than $500.”	Bring urgent orders to your team. Orders above your chosen amount trigger an email to the people responsible for following up.
Sending history	“Add an admin view of this month’s Resend emails and their latest delivery status.”	Check delivery inside your app. An admin page lists Resend messages and their latest status, making unsuccessful sends visible alongside other app activity.

Connect Resend to Mythos

Your workspace must allow you to create App + chat connections. If you cannot set one up, ask your workspace owner or admin to check your access.

A saved Resend connection can be used by the projects linked to it. If you already have a connection, open it instead of setting it up again.

Before you start

You will need:

A Resend account.
A domain verified in Resend to send to other people. The test sender is only for emailing your own Resend account address.
A Resend API key with Full access.
Permission to create connections in your Mythos workspace.

Resend charges for email usage under your Resend plan. Connecting it to Mythos does not include a separate email allowance.

1. Create your Resend API key

The key gives Mythos access to your Resend account. Full access keys can manage resources across the account; Sending access keys are limited to sending email. Choose Full access for Mythos: it is required to check the connection and work with domains and email status. A sending-only key cannot complete this setup.

Open API Keys. Sign in to Resend and go to API Keys.
Create the key. Select Create API Key, give it a recognizable name such as Mythos email, and choose Full access.
Save the value. Copy the new key to a secure place. You cannot view its value again after creation. Resend keys begin with re_.

Treat this key as a password. Paste it into the connection’s API Key field, not a chat message or a public file.

For details, see Resend’s API key guide and API reference.

2. Set up the connection in Mythos

Open Resend. From the Dashboard, open Connectors and select Resend. The setup form opens for your first connection.
Name the connection. Enter a Display name, such as Store email. This name helps you recognize the connection in Mythos.
Add your key. Paste the key you created into API Key.
Choose access. Sharing starts as Private. Leave it private, or choose Share with others to give workspace members access. Use Share with workspace if everyone in the workspace should be able to use it.
Connect. Click Connect. Mythos checks the key before saving the connection. This check does not send an email.

To use it in an app, open Chat actions (+) → Project connectors in your project, select the saved Resend connection, and click Use in this project. Then ask Mythos to add the email workflow you want. Sharing the connection with people and linking it to a project are separate choices.

Send email from your domain

For email to reach people other than yourself, Resend needs a verified sending domain. Its test sender, onboarding@resend.dev, only delivers to the address associated with your Resend account.

Add your domain in Resend Domains and follow the verification instructions. You publish the required DNS records through the service that manages your domain. Mythos can also add a domain to Resend, show the required records, and ask Resend to check them after you have added them.

Include your sender address in the prompt, for example orders@example.com, so Mythos uses the address you intend. Once the flow is built, try it with an inbox you control and check that the message arrives.

If a message is rejected, check the saved key, the sender address, and the domain’s verification status. Review the email in Resend to see its delivery status. If sending stops after a connection change, also check that the project is still linked.

What the connector does not cover

Changing DNS records for you. You still add the records at your DNS provider, even when Mythos helps prepare or check the domain in Resend.
Receiving delivery webhooks automatically. Configure Resend webhooks separately for your app’s own endpoint, or use email-status lookups.
A separate Resend login for every app user. The linked projects use the account saved in the connection.

Manage a saved connection

Open Connectors, select Resend, and open the saved connection.

Unlink projects removes access for the selected projects. The connection remains available to its other linked projects.
Disconnect stops the connection across its linked projects. To restore email features, connect Resend again, link the project, and ask Mythos to set them up again.

To use a replacement API key, disconnect the old connection, connect Resend with the new key, and link your project again. Ask Mythos in Build to set up the affected email features before relying on them to send email.