mailsend

mailsend

mailsend lets an agent run the sending side of a Resend account: send a message and look it back up, set up a sending domain and start its DNS verification, mint or retire API keys, and keep audiences and their contacts in order. Each operation is one call against the Resend REST API, and the API's JSON answer comes back as-is. It runs from the command line or as an MCP server for agents.

A Resend API key is required. Put it in the RESEND_API_KEY environment variable; the key is sent to the API as a Bearer token and never appears in output. When the variable is missing, every operation fails with an error that names it.

Install

npx @reneturcios/mailsend list-domains

Or run the container image:

docker run -i -e RESEND_API_KEY ghcr.io/cloudcorprecords/mailsend

The container defaults to the MCP server (see below). Pass CLI arguments to use it as a CLI instead.

CLI

export RESEND_API_KEY="your API key"

mailsend send --from "Acme <[email protected]>" --to [email protected] \
  --subject "Welcome" --text "Hello there"
mailsend list-emails --limit 10
mailsend list-domains
mailsend list-audiences

mailsend --version

Exit codes: 0 on success, 1 when an API call fails (including a missing RESEND_API_KEY), 2 for usage errors.

MCP server

One bin serves both faces. The mcp subcommand starts a stdio MCP server:

npx -y @reneturcios/mailsend mcp

MCP client configuration:

{
  "mcpServers": {
    "mailsend": {
      "command": "npx",
      "args": ["-y", "@reneturcios/mailsend", "mcp"],
      "env": { "RESEND_API_KEY": "your API key" }
    }
  }
}

Tools

Tool	Input	What it does
send_email	from, to (array), subject (required); html, text, cc, bcc, reply_to (optional)	Send an email.
list_emails	limit (integer, optional)	List sent emails.
get_email	id (required)	Get one sent email by ID.
create_domain	name (required), region (optional)	Create a sending domain.
list_domains	—	List sending domains.
get_domain	id (required)	Get one domain, including its DNS records.
verify_domain	id (required)	Start DNS verification for a domain.
delete_domain	id (required)	Delete a sending domain.
create_api_key	name (required), permission, domain_id (optional)	Create an API key.
list_api_keys	—	List API keys.
delete_api_key	id (required)	Delete an API key.
create_audience	name (required)	Create an audience.
list_audiences	—	List audiences.
create_contact	audience_id, email (required); first_name, last_name, unsubscribed (optional)	Add a contact to an audience.
list_contacts	audience_id (required), limit (optional)	List contacts in an audience.

This is a documented core subset of the Resend platform surface. The hosted Resend MCP also covers broadcasts, templates, webhooks, segments, topics, contact properties, batch sending, and received (inbound) email; those groups are not implemented here.

Development

npm install
npm run build   # tsc -> dist/
npm test        # node test runner over test/*.test.ts, no network (fake fetch fixtures)
npm run dev     # run the CLI from source via tsx

License

MIT — see LICENSE.