MailerSend API Authentication

How to authenticate MailerSend API requests: one Bearer API key plus a connectionId. MindCloud stores your API key securely — set it once, never resend it.

Every MailerSend API request through MindCloud needs two things: a MindCloud API Key and a connectionId for your MailerSend account. This page covers both, plus exactly how to send them, so you do not need to visit any other page to get authenticated.

Steps to authenticate

Create a MindCloud account at app.mindcloud.co if you do not already have one.
Generate a MindCloud API Key in API Keys. This is the Bearer token you send on every request. Keep it on your server.
Create a MailerSend connection in Connections. MailerSend uses an API key. You generate the key in your MailerSend account, then paste it in when you create the connection — MindCloud stores it securely and never returns it in a response.
Copy the connection’s connectionId — you will send it on every request alongside your MindCloud API Key.

How requests are authenticated

Authentication has two layers. Your MindCloud API Key authenticates the request to MindCloud, sent as a Bearer token in the Authorization header. The connectionId selects the connected MailerSend account that should run the action. MindCloud stores and refreshes the MailerSend credentials behind that connection, so you never send provider tokens with your requests.

Pass connectionId in the query string for GET and DELETE actions, and in the JSON body for POST, PUT, and PATCH actions.

For example, calling List Messages with an MailerSend connection looks like this:

curl --request POST \
  --url "https://connect.mindcloud.co/v2/universal/apps/mailerSend/actions/list-messages/run" \
  --header "Authorization: Bearer $MINDCLOUD_API_KEY" \
  --header "Content-Type: application/json" \
  --data '{
  "connectionId": "$CONNECTION_ID",
  "arguments": {}
}'

The Authorization: Bearer <your MindCloud API Key> header authenticates you to MindCloud; the connectionId tells MindCloud which MailerSend account to run the action against. Missing or invalid Authorization returns 401, and a missing or mismatched connectionId returns 400.

Connect your MailerSend API token

You need access to a MailerSend account and a sending domain or sender identity that is allowed to use the API.

Sign in to MailerSend
Open MailerSend and sign in to the workspace that owns the sending domain you want to use for this connection.
Open the API token settings
In the MailerSend app, go to Integrations, open MailerSend API, and choose the option to manage API tokens.
Create a new token
Create a token for the sending domain you want this connection to use, then grant the permissions required for the MailerSend actions you plan to run.
Copy the token immediately
Copy the token and store it securely before you leave the creation flow. MailerSend does not show the full token again later.
Paste the token into this connection
Return here and paste the token into the API key field for this MailerSend connection.

Keep your key safe

Keep your MindCloud API Key on your server; do not ship it in browser code, mobile apps, public repositories, or logs. Anyone with the key can call the Universal API as your MindCloud account, across every connection you have created.