Hosted Email Deliverability MCP for AI Agents
If you're searching for an email deliverability MCP that's hosted and ready to use, marginal runs the server for you. Your AI agent connects over a single endpoint and starts launching subject line A/B tests, sending managed campaigns, and reading back open and click metrics — without you standing up any infrastructure.
What "hosted" means for an email MCP server
Self-hosting an MCP server means provisioning a process, securing it, and keeping it online. marginal skips all of that. The email MCP server lives at https://marginal.sh/mcp and authenticates with a Bearer API key, so the only thing you maintain is the key itself.
Because the server is managed, deliverability concerns like send reputation, tracking pixels, and click redirects are handled on marginal's side. Your agent calls tools and gets results — it doesn't babysit a mail stack.
- Single endpoint: https://marginal.sh/mcp
- Auth via Bearer API key (marg_live_...)
- No self-hosted MCP server to deploy or patch
- Managed sends with open and click tracking built in
Deliverability signals you can read from the agent
Deliverability isn't a single number — it's the pattern of opens and clicks you see once mail lands. marginal exposes those signals through MCP tools so an AI agent email marketing workflow can react to real engagement, not guesses.
Each subject line A/B test reports within-test lift, so you can tell whether a variant is genuinely outperforming or just noisy. The recommend_next tool turns that data into a concrete suggestion for what to send next.
- generate_variants — draft subject line candidates
- launch_test — start a managed A/B test send
- get_results — pull open/click rates and within-test lift
- recommend_next — get a data-backed next step
Connecting your agent
marginal works with the MCP clients teams already use: Cursor, Claude Desktop, Claude Code, OpenAI Codex, Windsurf, Cline, Continue, and Zed. Add the hosted endpoint and API key to your client config and the four tools appear automatically.
From there, a typical loop is generate variants, launch a subject line A/B test, wait for engagement to accumulate, then read results and let the agent recommend the next iteration — all without leaving your editor or chat client.
Start without infrastructure
The free tier includes 100 experiments per month, which is enough to validate a hosted email deliverability MCP workflow before scaling. Point your agent at the endpoint, run a test, and watch the metrics flow back.
Full tool references and client setup live in the docs at https://marginal.sh/docs/.
- 100 experiments/month on the free tier
- Registry: sh.marginal/mcp
- Endpoint: https://marginal.sh/mcp
- Docs: https://marginal.sh/docs/
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