How to Send Email from a Cursor Agent
If you're already living in Cursor, you can let your agent handle email campaigns directly — drafting subject lines, launching tests, and reading results. marginal is a hosted email MCP server that gives your Cursor agent the tools to send email and measure what actually performs.
Why send email from your Cursor agent
Most email workflows live outside the editor: a separate dashboard, a separate copy doc, a separate analytics tab. When you wire marginal into Cursor as an MCP server, the agent gains four tools — generate_variants, launch_test, get_results, and recommend_next — so the whole loop happens in one place.
That means you can describe a campaign in plain language and have the Cursor agent generate subject line variants, launch a managed send, and report back on opens and clicks without you context-switching.
- Draft and test subject lines from a natural-language prompt
- Run a subject line A/B test with managed sends
- Pull open/click tracking and within-test lift metrics
- Get a recommended next step based on the winning variant
Connecting marginal to Cursor
marginal is hosted, so there is no self-hosted MCP server to run. You point Cursor at the endpoint https://marginal.sh/mcp and authenticate with a Bearer API key that starts with marg_live_. Once connected, the marginal tools appear to your Cursor agent automatically.
Add the server through Cursor's MCP settings, paste your key, and confirm the connection. From there the agent can call any of the four tools as part of a normal conversation.
- Registry: sh.marginal/mcp
- Endpoint: https://marginal.sh/mcp
- Auth: Bearer API key (marg_live_...)
- Setup docs: https://marginal.sh/docs/
Running a subject line A/B test from Cursor
A typical flow starts with generate_variants to create several subject line candidates from your prompt. Then launch_test sends them as a managed test to your audience. As results come in, get_results returns open and click data plus within-test lift so you can see which variant is winning, and recommend_next suggests how to follow up.
Because this is AI agent email marketing inside your editor, you can iterate quickly — ask the agent to refine the angle, regenerate variants, and relaunch without leaving Cursor.
- generate_variants — produce subject line options
- launch_test — run the subject line A/B test as a managed send
- get_results — review opens, clicks, and lift
- recommend_next — get a data-backed next move
Getting started for free
The free tier includes 100 experiments per month, which is plenty for testing the workflow and running real campaigns from your Cursor agent. The same email MCP server also works with Claude Desktop, Claude Code, Windsurf, Cline, Continue, Zed, and OpenAI Codex, so your setup carries across tools.
Start small: connect marginal, run one subject line A/B test from Cursor, and let the results guide your next send.
- 100 experiments/month on the free tier
- Same tools across Cursor and other MCP clients
- Hosted — no infrastructure to maintain
Get started with marginal
marginal is a hosted email marketing MCP server at marginal.sh. Sign up free, create an API key, and connect https://marginal.sh/mcp from Cursor, Codex, or Claude Desktop.
- 100 experiments/month on the free tier
- Four MCP tools: generate_variants, launch_test, get_results, recommend_next
- Listed in the MCP Registry as sh.marginal/mcp