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2026-07-31 · MailAnvil Team

How the New MCP 2025-07-28 Spec Changes Email API Integration — Provider Comparison

On July 28, 2026, the Model Context Protocol (MCP) released a new specification. It's the biggest change since MCP went mainstream in early 2026 — and it has direct implications for how email APIs integrate with AI agents.

Let's break down what changed, what it means for email providers, and how the major players stack up.

What the 2025-07-28 spec changed

The headline change: no handshake or sessions. The spec replaces the connection lifecycle with a simpler stateless model.

Aspect Before (2024 spec) After (2025-07-28)
Transport WebSocket required HTTP POST (streaming optional)
Handshake Client/server capability negotiation No handshake. Capabilities in headers
Sessions Stateful session per connection Stateless — every request is self-contained
Headers MCP-Version only MCP-Protocol-Version, Mcp-Method, Mcp-Name
Streaming Native SSE Server-sent events via Accept: text/event-stream

The new spec essentially makes MCP work more like REST — every call is independent, headers carry the metadata, and the server doesn't need to remember who you are between requests.

What this means for email APIs

For email providers with MCP support, this spec changes the integration model:

Before: AI agent connects via WebSocket, negotiates capabilities, maintains a session. Every email send requires an active WebSocket connection.

After: AI agent sends an HTTP POST with MCP-Protocol-Version: 2025-07-28 and Mcp-Method: tools/call. The email provider processes it and responds. No session, no WebSocket, no complexity.

For AI SaaS builders, this means:

  1. No persistent connections — your AI agent can send email on-demand without maintaining a WebSocket
  2. Easier debugging — every request is curl-friendly
  3. Lower latency — no connection setup overhead on cold starts
  4. Better serverless compatibility — HTTP-only works natively with Edge Functions, Cloudflare Workers, AWS Lambda

Provider comparison

Here's how the major email MCP providers handle the new spec:

Feature Resend Mailgun Mailtrap MailAnvil
MCP type Remote (hosted) Open-source self-hosted Remote (hosted) Native (built-in)
2024 spec ✅ ✅ ✅ ✅
2025-07-28 spec TBD TBD TBD ✅ (day 1)
Sessionless HTTP ❌ WebSocket ❌ SDK-only ❌ WebSocket ✅ HTTP POST
Serverless-native ❌ ❌ ❌ ✅ CF Workers
IDR pricing ❌ ❌ ❌ ✅ Rp149rb/10K
QRIS/GoPay ❌ ❌ ❌ ✅
Bahasa docs ❌ ❌ ❌ ✅
Auto-DKIM (CF DNS) ❌ ❌ ❌ ✅

Resend

Resend's MCP is a hosted remote server. It uses the 2024 spec with WebSocket transport. Well-documented, developer-friendly, but requires a persistent connection. No word yet on 2025-07-28 support. Resend targets global developers — no local pricing for Indonesia.

Mailgun

Mailgun's MCP is open-source (npx @mailgun/mcp-server). It runs locally as a subprocess — not ideal for remote AI agents or serverless environments. The open-source model means you manage the MCP server yourself. Good for teams that want control, but adds operational overhead.

Mailtrap

Mailtrap's MCP covers both testing (sandbox) and production sending. Uses the 2024 WebSocket spec. Their strength is the testing workflow — spam analysis, previews, and debugging. But the MCP integration is add-on, not native to the API layer.

MailAnvil

MailAnvil is the only MCP-native email API. MCP is built into the API layer itself — every endpoint is also an MCP tool. With Cloudflare Workers, there's no persistent server to manage. MailAnvil supports the 2025-07-28 spec day one: HTTP POST with header-based capability declaration, sessionless, stateless.

The send_email tool responds to:

POST /mcp HTTP/1.1
MCP-Protocol-Version: 2025-07-28
Mcp-Method: tools/call

{"jsonrpc":"2.0","id":1,"method":"tools/call",
 "params":{"name":"send_email","arguments":{...}}}

No WebSocket. No session. One HTTP call.

Why this matters for Indonesian developers

Most email APIs charge in USD. For Indonesian SaaS startups sending 10,000 emails/month: - Resend: $20/mo (~Rp 325,000) - Mailgun: $35/mo (~Rp 570,000) - Mailtrap: $15/mo (~Rp 244,000) - MailAnvil: Rp 149,000/mo

With the 2025-07-28 spec making MCP simpler (HTTP-only, no WebSocket), the barrier to MCP-native email drops even further. You don't need WebSocket support in your environment. You don't need to maintain a session. Your AI agent just POSTs to the MCP endpoint and gets back a response.

Getting started with MCP 2025-07-28 + MailAnvil

{
  "mcpServers": {
    "mailanvil": {
      "url": "https://mcp.mailanvil.com/mcp",
      "headers": {
        "Authorization": "Bearer re_..."
      }
    }
  }
}

That's it. Your AI agent discovers the tools automatically: send_email, get_email_logs, list_domains, list_templates, get_usage_stats.

For curl (new spec syntax):

curl https://mcp.mailanvil.com/mcp \
  -H "MCP-Protocol-Version: 2025-07-28" \
  -H "Mcp-Method: tools/call" \
  -H "Authorization: Bearer re_..." \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call",
       "params":{"name":"send_email",
         "arguments":{"to":["[email protected]"],
           "subject":"From MCP 2025-07-28",
           "html":"<p>Hello from the new spec!</p>"}}}}'

Bottom line

The MCP 2025-07-28 spec makes email API integration simpler, faster, and more serverless-friendly. Among email providers with MCP support, only MailAnvil is native, sessionless, and runs on Edge Workers.

If you're building an AI SaaS — especially for the Indonesian market — that combination of MCP-native, IDR pricing, and no-infrastructure backend is hard to beat.

Next steps

MailAnvil — Transactional Email API for Indonesian developers. IDR pricing, QRIS/GoPay, Bahasa docs. Built on Cloudflare Workers + AWS SES.